© 2014 American Society of Plant Biologists

Potassium: Potash, from the ashes

in the pot

Regulates

stomatal

conductance,

photosynthesis

and transpiration

Maintains turgor

and reduces wilting

Strengthens

cell walls Maintains ionic

balance Stimulates

photosynthate

translocation

Enhances

fertility

Promotes stress

tolerance

See Wang, M., Zheng, Q., Shen, Q. and Guo, S. (2013). The critical role of potassium in plant stress response. Intl. J. Mol. Sci. 14: 7370-7390; Sin Chee Tham /Photo; Purdue extension; Onsemeliot.

Symptoms of

potassium deficiency

[K+] in soil = ~0.1 – 1 mM

[K+] in plant cell

cytoplasm = ~100 mM

Potassium is an essential macronutrient

Regulates

enzyme activities

© 2014 American Society of Plant Biologists

Potassium fertilizers are mined from

underground reserves as “potash”

Almost half of the world’s reserved of potash

are found in Saskatchewan, Canada

Potash is a term that encompasses

many forms of potassium:

• KCl (potassium chloride, aka sylvite)

• K2SO4 (potassium sulfate)

• K2CO3 (potassium carbonate)

• K2Ca2Mg(SO4)4·2H2O (polyhalite)

• etc.

Canada Potash; Lmbuga

KCl, sylvite

For historical reasons, potash

is measured in units of K2O

equivalents, even though it is

rarely found in the form of K2O

© 2014 American Society of Plant Biologists

Potash provides K for fertilizers,

which supplement natural sources

manure

decomposition

Terrestrial

cycle: Plant /

Animal / Soil Underground reserves

Water with

dissolved K+

salts returned

to surface

Water

pumped

underground

Salts

recovered by

evaporation

90 – 98%

insoluble

minerals

1 – 3%

exchangeable

salts

0.1 – 0.2% soil

solution K+

Potash

fertilizer

application

Adapted from International Potash Institute

© 2014 American Society of Plant Biologists

Potash prices can be volatile and

there are few suppliers

1.06 cm

Canada is #1

in production

(11.2 Mt) and

reserves

(4,400 Mt)

Russia is #2

in production

(7.4 Mt) and

reserves

(3,300 Mt)

Brazil

3.2 Mt

210 Mt

Chile

0.8 Mt

130 Mt

US

1.1 Mt

130 Mt

China

3.2 Mt

210 Mt

Belarus

5.5 Mt

750 Mt

World

reserves

9500 Mt

World

production

(2011)

37 Mt

Jordan

1.4 Mt

40 Mt

Israel

2.0 Mt

40 Mt

Germany

3.3 Mt

150 Mt

Spain

0.4 Mt

20 Mt

UK

0.4 Mt

22 Mt

Adapted from International Potash Institute

© 2014 American Society of Plant Biologists

Potassium is an essential plant

nutrient

Reprinted from Maathuis, F.J.M. (2009). Physiological functions of mineral macronutrients. Curr. Opin. Plant Biol. 12: 250-258 with permission from Elsevier.

K+ uptake

involves high

and low affinity

transporters

K+ is a counter ion for

negatively charged molecules

including DNA and proteins

K+ is a cofactor for

some enzymes

As the major cation in

the vacuole, K+

contributes to cell

expansion and

movement, including

that of guard cells

K+ moves in and

out of the vacuole

through specific

transporters

© 2014 American Society of Plant Biologists

Early studies of potassium uptake in

plants: Biphasic uptake

Epstein, E., Rains, D.W., and Elzam, O.E. (1963). Resolution of dual mechanisms of potassium absorption by barley roots. Proc. Natl. Acad. Sci. USA. 49: 684 – 692;

Gierth, M. and Mäser, P. (2007). Potassium transporters in plants – Involvement in K+ acquisition, redistribution and homeostasis. FEBS Lett. 581: 2348-2356.

KCl (mM)

Low affinity

transport

High affinity

transport

Epstein et al showed

two phases of K+

uptake in barley roots

K+ K+ H+

H+

ATP

2 x H+

2 x ATP

Low affinity

transport

High affinity

transport

K+ uptake from low [K+]ext

requires more energy than

when [K+]ext is higher

Co-transporter

mediated

Channel

mediated

© 2014 American Society of Plant Biologists

K+ mobilization is critical for K+ use

efficiency

Adapted from Amtmann, A., and Leigh, R. (2010). Ion homeostasis. In Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic

Foundation, A. Pareek, S.K. Sopory, H.J. Bohnert and Govindjee (eds) (Dordrecht, The Netherlands: Springer), pp. 245 – 262.

Cytosol

Vac.

Supraoptimal K+

can be stored in

the vacuole As K+ becomes

limiting, it becomes

preferentially allocated

to the cytosol

© 2014 American Society of Plant Biologists

K+ mobilization is critical for K+ use

efficiency

Cytosol

Vac.

Prioritized

Non-

Prioritized

As K+ becomes

limiting, it becomes

preferentially allocated

to the cytosol

K+ can be remobilized

from less essential tissues

into prioritized tissues

such as growing and

photosynthetic tissues

Adapted from Amtmann, A., and Leigh, R. (2010). Ion homeostasis. In Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic

Foundation, A. Pareek, S.K. Sopory, H.J. Bohnert and Govindjee (eds) (Dordrecht, The Netherlands: Springer), pp. 245 – 262.

© 2014 American Society of Plant Biologists

Summary: Potassium uptake,

transport and regulation

• Potassium is an essential macronutrient required

in large amounts

• Potassium uptake involves low and high affinity

transporters

• K+ uptake, transport and remobilization are

regulated extensively to ensure that the plant’s

critical tissues are preferentially supported

© 2014 American Society of Plant Biologists

Sulfur: Clean air can lead to

deficient plants

International Society of Arboriculture; Robert L. Anderson, USDA Forest Service; D'Hooghe, P., Escamez, S., Trouverie, J. and Avice, J.-C. (2013). Sulphur limitation provokes physiological and leaf proteome changes

in oilseed rape that lead to perturbation of sulphur, carbon and oxidative metabolisms. BMC Plant Biol. 13: 23. Hay and Forage.

Sulfur

dioxide

damage

Until recently, sulfur dioxide emission from

fossil fuel combustion led to acid rain and

extensive damage to vulnerable plants

Eliminating S from air

pollution uncovered

crop plant

deficiencies,

particularly in oilseed

rape and wheat

© 2014 American Society of Plant Biologists

Sulfur can be found in many

inorganic forms Species Name Oxidation

State

S2-, H2S, R-SH Sulfide -2

S0, S8 Sulfur 0

SO2 Sulfur dioxide (toxic gas) +4

SO3- Sulfite +4

SO42- Sulfate +6

Plants take up sulfur from soil as SO42- and to a

lesser extent from the atmosphere as SO2 or H2S

Organic S

R-SH

SO42-

S0

H2S

Sulfur

deposits

SO3-

© 2014 American Society of Plant Biologists

Plants are an important part of the

global sulfur cycle Atmospheric pool of sulfur – mostly SO2 (sulfur dioxide)

Combustion

of fossil fuels

Prokaryotic oxidation

R-SH

manure

Assimilation

by plants decomposition

SO2 SO42- H2O

O2

SO42- S

Volcanic activity

SO42-

Acid

rain*

*Since the 1980s,

SO2 emissions and

SO42- precipitation

have been declining

H2S

Prokaryotic reduction

See for example Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic

organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.

© 2014 American Society of Plant Biologists

Sulfur is an essential macronutrient

in amino acids & other compounds

HS-CH2-CH-COOH

NH2

H3C-S-CH2-CH2-CH-COOH

NH2

Methionine (Met)

Cysteine (Cys)

Amino

acids

Cys Glutathione Glutathione is an amino

acid derivative involved

in Redox reactions

Oxidation /reduction,

metal transport and

detox

S

Allicin (garlic flavor)

Allyl-isothiocyanate

(horseradish flavor)

Flavor or

odor

SH

O

Mercapto-p-

menthan-3-one

(blackcurrant)

S S

S S

Defense Glucosinolates are

anti-herbivores

Camalexin is a

defense compound

induced by pathogens

S

S

McGorrin, R.J. (2011). The significance of volatile sulfur compounds in food flavors. Volatile Sulfur Compounds in Food. ACS Symposium Series, Vol. 1068: 3-31

© 2014 American Society of Plant Biologists

Sulfate uptake occurs primarily

through SULTR transporters

Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773 with permission from Oxford University Press; Smith, F.W., Ealing,

P.M., Hawkesford, M.J. and Clarkson, D.T. (1995). Plant members of a family of sulfate transporters reveal functional subtypes. Proc. Natl. Acad. Sci. USA 92: 9373-9377. Rouached, H., Secco, D. and Arpat, A.B. (2009). Getting the most sulfate from

soil: Regulation of sulfate uptake transporters in Arabidopsis. J. Plant Physiol. 166: 893-902. Gojon, A., Nacry, P. and Davidian, J.-C. (2009). Root uptake regulation: a central process for NPS homeostasis in plants. Curr. Opin. Plant Biol. 12: 328-338.

In Arabidopsis, 12 genes

encode SULTR transporters that

fall into four groups

Most are 12-membrane spanning

SO42- / H+ co-transporters

SO42- H+

SO42- H+

Primary assimilation in roots occurs mainly

through SULTR1;1 and SULTR1;2

© 2014 American Society of Plant Biologists

In higher plants, SULTR transporters

effect inter-organelle movement

Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773; Gigolashvili, T. and Kopriva, S. (2014).

Transporters in plant sulfur metabolism. Frontiers in Plant Science. 5: 442. Rennenberg, H. and Herschbach, C. (2014). A detailed view on sulphur metabolism at the cellular and whole-plant level illustrates challenges in

metabolite flux analyses. J. Exp. Bot. 65 : 5711-5724.

Vacuole

Plastid

Cytosol

[SO42-] 6 – 75 mM

[SO42-] ≤ 10 μM

[SO42-] 1 – 11 mM

[SO42-]

4 – 12 mM

SO42- H+

SULTR

SO42-

H+

SULTR

SO42-

H+

STORAGE

SULTR

SO42-

S2-

Sulfate

reduction only

occurs in

plastids

© 2014 American Society of Plant Biologists

Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773 by permission of Oxford University Press.

S transporters

coordinate

long-distance

transport too

© 2014 American Society of Plant Biologists

Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.

Uptake

Adenosine 5'-phosphosulfate

5'-Phosphoadenosine

3'-phosphosulfate

Primary sulfur

metabolism (overview)

© 2014 American Society of Plant Biologists

Sulfate is assimilated by ATP

sulfurylase into APS

Sulfate ATP

+

Pyrophosphate

(PPi) Adenosine 5'-

phosphosulfate (APS)

+

ATP

sulfurylase

Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic

organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.

This reaction occurs in the

cytosol and plastid

© 2014 American Society of Plant Biologists

APS can enter two pathways for

primary or secondary reactions

Adenosine 5'-

phosphosulfate (APS)

APS

kinase

ATP

ADP

5'-Phosphoadenosine 3'-

phosphosulfate (PAPS)

Sulfated compounds,

glucosinolates

APS

reductase

Sulfite

reductase Sulfite

Sulfide

AMP

SO32- S2-

2 GSH

GSSG FdxRed

FdxOx

Cysteine

Located exclusively in plastids

Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic

organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.

© 2014 American Society of Plant Biologists

Sulfide is assimilated into cysteine

by the cysteine synthase complex

Reprinted from Jez, J.M. and Dey, S. (2013). The cysteine regulatory complex from plants and microbes: what was old is new again. Curr. Opin. Structural Biol. 23: 302-310 with permission from Elsevier.

O-acetylserine (OAS)

indicates cellular S

status: when S is low,

OAS accumulates

Adenosine 5'-

phosphosulfate (APS)

(thiol)lyase (OAS-TL)

Cysteine

synthase is a

complex of SAT

and OAS-TL,

and is present

in the cytosol,

plastid and

mitochondria

© 2014 American Society of Plant Biologists

Model for regulation of cysteine

synthesis by the CS complex

Reprinted from Jez, J.M. and Dey, S. (2013). The cysteine regulatory complex from plants and microbes: what was old is new again. Curr. Opin. Structural Biol. 23: 302-310 with permission from

Elsevier.Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.

When SO42- is available,

free OAS-TL dimers

produce cysteine

OAS is synthesized by SAT within

the cysteine synthase (CS) complex

SAT CS OAS-TL is inactive

within the CS complex

© 2014 American Society of Plant Biologists

Model for regulation of cysteine

synthesis by the CS complex

Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.

When SO42- is

unavailable, OAS

accumulates, causing the

CS complex to dissociate,

and decreasing the

activity of SAT. Thus, the

rate of production of OAS

decreases

Free SAT is deactivated

© 2014 American Society of Plant Biologists

Sulfur uptake and assimilation rates

are metabolically regulated

Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu.

Rev. Plant Biol. 62: 157-184; Davidian, J.-C. and Kopriva, S. (2010). Regulation of sulfate uptake and assimilation—the same or not the same? Mol. Plant. 3: 314-325. Yi, H., Galant, A., Ravilious, G.E., Preuss, M.L. and

Jez, J.M. (2010). Sensing sulfur conditions: Simple to complex protein regulatory mechanisms in plant thiol metabolism. Mol. Plant. 3: 269-279.

SO42-

out

SO42-

in

SULTR

APS

Reductase

Cys Synthase

SO3-

Cys

Transcriptional, post-

transcriptional and post-

translational / allosteric

regulation of transporters

Local sulfate levels

OAS

OAS

Allosteric interactions,

metabolic regulation

Reduced sulfur

(glutathione, Cys etc)

Light, carbon and

nitrogen reserves,

circadian rhythms etc)

Transcriptional regulation

of ATP sulfurylase and

adenosine 5'-

phosphosulfate (APS)

reductase (APR)

ATP

Sulfurylase

© 2014 American Society of Plant Biologists

SLIM (EIL3) coordinates many

transcriptional responses to S

Maruyama-Nakashita, A., Nakamura, Y., Tohge, T., Saito, K. and Takahashi, H. (2006). Arabidopsis SLIM1 is a central transcriptional regulator of plant sulfur response and metabolism. Plant Cell. 18: 3235-3251.

SLIM = Sulfur

Limitation

Red, pink =

up-regulated by

S-deficiency

Blue =

down-regulated

by S-deficiency

Thioglucosidase activity

(increased by S-

deficiency) liberates S

for recycling

© 2014 American Society of Plant Biologists

Addressing S deficiency in plants

D'Hooghe, P., Escamez, S., Trouverie, J. and Avice, J.-C. (2013). Sulphur limitation provokes physiological and leaf proteome changes in

oilseed rape that lead to perturbation of sulphur, carbon and oxidative metabolisms. BMC Plant Biol. 13: 23. Hay and Forage.

S sufficient S deficient With stricter laws

on S emissions,

less S enters

soils and plants

are more prone

to S deficiency

Soil can be

augmented with

elemental sulfur,

ammonium sulfate or

other fertilizers

© 2014 American Society of Plant Biologists

Summary: Sulfur uptake and

metabolism

• Found in many redox forms and can be assimilated from

atmosphere

• Deficiency more common with cleaner air

• SULTR transporter family primarily involved in uptake

and transport

• Uptake and assimilation into organic forms subject to

positive and negative regulation

© 2014 American Society of Plant Biologists

Magnesium: The “forgotten

element”

Didier Descouens; Ra’ike; chensiyuan; James St. John

Mg in solution is a

divalent cation Mg2+

Soil magnesium is a

result of rock

weathering and Mg2+

from seawater

Serpentine

3MgO*2SiO2*2H2O

The Dolomite Mountains are

named for the mineral dolomite

MgCO3*CaCO3

Magnesite

MgCO3

© 2014 American Society of Plant Biologists

Magnesium is a cofactor for many

enzymes and central to chlorophyll Mg2+ is a counter

ion for the negative

charges of ATP

Mg2+

stabilizes

ribosome

3D structure

Mg2+ is central

to chlorophyll

Mg2+ is an essential

activator for many

enzymes including

Rubisco

Jensen, R.G. (2000). Activation of Rubisco regulates photosynthesis at high

temperature and CO2. Proc. Natl. Acad. Sci. USA 97: 12937-12938.

© 2014 American Society of Plant Biologists

Mg deficiency interferes with

photosynthesis & C transport

Reused with permission from Wiley from Cakmak, I. and Kirkby, E.A. (2008). Role of magnesium in carbon partitioning and alleviating photooxidative damage. Physiol. Plant.

133: 692-704; See also Verbruggen, N., and Hermans, C. (2013). Physiological and molecular responses to magnesium nutritional imbalance in plants. Plant Soil. 368: 87 – 99.

Effects of Mg deficiency

One symptom of Mg

deficiency is high-light

induced chlorosis

© 2014 American Society of Plant Biologists

Magnesium transporters move Mg2+

across membranes

Reproduced from Hermans, C., Conn, S.J., Chen, J., Xiao, Q. and Verbruggen, N. (2013). An update on magnesium homeostasis mechanisms in plants. Metallomics. 5: 1170-1183 with permission of The Royal Society

of Chemistry; Reprinted by permission from Macmillan Publishers Ltd Hattori, M., Tanaka, Y., Fukai, S., Ishitani, R. and Nureki, O. (2007). Crystal structure of the MgtE Mg2+ transporter. Nature. 448: 1072-1075.

There are two known

classes of Mg transporters:

MRS/MGT

MHX (Mg/H+ exchanger)

Proposed structure and

mechanism of an MRS-type

transporter

Mg transporters are

different from other cation

transporters but conserved

across life domains

© 2014 American Society of Plant Biologists

Magnesium uptake is mediated by

the MRS / MGT family

Gebert, M., Meschenmoser, K., Svidová, S., Weghuber, J., Schweyen, R., Eifler, K., Lenz, H., Weyand, K. and Knoop, V. (2009). A root-expressed magnesium transporter of the MRS2/MGT gene family in Arabidopsis

thaliana allows for growth in low-Mg2+ environments. Plant Cell. 21: 4018-4030. Mao, D., Chen, J., Tian, L., Liu, Z., Yang, L., Tang, R., Li, J., Lu, C., Yang, Y., Shi, J., Chen, L., Li, D. and Luan, S. (2014). Arabidopsis

transporter MGT6 mediates magnesium uptake and is required for growth under magnesium limitation. Plant Cell. 26: 2234-2248.

MGT6 RNAi WT

MGT6 is induced in roots

by low Mg and required

for efficient Mg uptake

© 2014 American Society of Plant Biologists

Aluminum toxicity is minimized by

increased Mg uptake

Delhaize, E., and Ryan, P.R. (1995). Aluminum toxicity and tolerance in plants. Plant Physiol. 107: 315 – 321. Bose, J., Babourina, O. and Rengel, Z.

(2011). Role of magnesium in alleviation of aluminium toxicity in plants. J. Exp. Bot. 62: 2251-2264, by permission of Oxford University Press.

Al tolerant

Al sensitive

Al inhibits growth,

especially in low pH soils

where it is most soluble

Elevated Mg soil

levels or uptake

can minimize Al

toxicity mainly

through

competition for

uptake and

molecular

interactions

© 2014 American Society of Plant Biologists

Mg deficiency in plants contributes

to Mg deficiency in animals

Peggy Greb USDA

Rapidly growing spring grass can be low

in Mg, so grass-fed cattle can experience

hypomagnesemia, a sometimes fatal

condition called grass tetany

Mg2+

To ensure adequate dietary

Mg2+, human diets should

include nuts, legumes,

leaves and whole grains

© 2014 American Society of Plant Biologists

Summary: Magnesium

• Rarely limiting for plant growth

• Mg2+ transporters are different from other cation

transporters, but conserved across life domains

• Elevated Mg2+ uptake can mitigate Al3+ toxicity

• Humans and animals can suffer Mg deficiency if dietary

sources are deficient

© 2014 American Society of Plant Biologists

Calcium: Low free cytosolic levels &

functions in apoplast / vacuole

Capoen, W., Den Herder, J., Sun, J., Verplancke, C., De Keyser, A., De Rycke, R., Goormachtig, S., Oldroyd, G. and Holsters, M. (2009). Calcium spiking patterns and the role of the calcium/calmodulin-dependent

kinase CCaMK in lateral root base nodulation of Sesbania rostrata. Plant Cell. 21: 1526-1540. Bose, J., Pottosin, I., Shabala, S.S., Palmgren, M.G. and Shabala, S. (2011). Calcium efflux systems in stress signalling and

adaptation in plants. Front. Plant Sci. 2: 85. Persson, S., Caffall, K.H., Freshour, G., Hilley, M.T., Bauer, S., Poindexter, P., Hahn, M.G., Mohnen, D. and Somerville, C. (2007). The Arabidopsis irregular xylem8 mutant

is deficient in glucuronoxylan and homogalacturonan, which are essential for secondary cell wall integrity. Plant Cell. 19: 237-255.

Middle lamella

Primary wall Secondary

wall

2 μm

Calcium

stabilizes pectin

in middle lamella

of cell walls

Cytosolic Ca2+

oscillations are

second

messengers in

diverse responses

© 2014 American Society of Plant Biologists

90% of the plant’s calcium can be in

the form of calcium oxalate crystals

Webb, M.A. (1999). Cell-mediated crystallization of calcium oxalate in plants. Plant Cell. 11: 751-761; Franceschi, V.R. and Nakata, P.A. (2005). Calcium oxalate in

plants: Formation and Function. Annu. Rev. Plant Biol. 56: 41-71. Kostman, T.A., Tarlyn, N.M., Loewus, F.A. and Franceschi, V.R. (2001). Biosynthesis of l-ascorbic

acid and conversion of carbons 1 and 2 of l-ascorbic acid to oxalic acid occurs within individual calcium oxalate crystal idioblasts. Plant Physiol. 125: 634-640.

Idioblasts are specialized

cells that form calcium

oxalate crystals and are

illuminated by polarized light (RI = raphide idioblast

DI = druse idioplast)

• The crystals are

formed by

specialized cells

called idioblasts

• Calcium oxalate

crystals can function

in defense

• Calcium oxalate

crystals also can

sequester excess

calcium

Prismatic

crystals from

bean seed coat

Druse crystals

from velvet leaf

(Abutilon

theophrasti)

Bundle of

raphide crystals

from grape leaf

© 2014 American Society of Plant Biologists

Plants maintain very low levels of

free cytosolic Ca2+

Stael, S., Wurzinger, B., Mair, A., Mehlmer, N., Vothknecht, U.C. and Teige, M. (2012). Plant organellar calcium signalling: an emerging field. J. Exp. Bot. 63: 1525-1542 by permission of Oxford University Press .

The concentration of

free Ca2+ is ~ 10,000

fold lower in the

cytosol than the

apoplast

The challenge at the

plasma membrane is

to maintain low free

internal Ca2+ (in

contrast to the situation

for most other

nutrients)

© 2014 American Society of Plant Biologists

Ca2+ transport systems include

channels, pumps and antiporters

Kudla, J., Batistič, O. and Hashimoto, K. (2010). Calcium signals: The lead currency of plant information processing. Plant Cell. 22: 541-563.

© 2014 American Society of Plant Biologists

Calcium deficiency causes cell wall

defects and sometimes cell death

White, P.J. and Broadley, M.R. (2003). Calcium in plants. Ann. Bot. 92: 487-511. Maine.gov; David B. Langston, University of Georgia; University of Georgia Plant Pathology Archive Bugwood.org

Ca2+

Calcium is

translocated in the

xylem (apoplast)

but not the phloem

(symplast),

meaning that it

cannot be

remobilized when

external supplies

are limited

Ca2+ deficiency in growing tissues causes

weakness and death, leading to blossom

end rot (left), tip burn (right) and bitter pit

(bottom). Ca2+ deficiency also can result

from a low rate of transpiration.

© 2014 American Society of Plant Biologists

Calcium contributes to pectin

crosslinking and stabilization

Sundar Raj AA, Rubila S, Jayabalan R, Ranganathan TV (2012) A review on pectin: Chemistry due to general properties of pectin and its pharmaceutical uses. 1:550 doi:10.4172/scientificreports.550 (adapted from

Axelos and Thibault, 1991). Hepler, P.K. and Winship, L.J. (2010). Calcium at the cell wall-cytoplast interface. J. Integr. Plant Biol. 52: 147-160, with permission from Wiley.

Pectin is found in the middle

lamella and the cell wall of a

growing pollen tube

Middle lamella

Pectin is a

galacturonic acid

polymer. Calcium

stabilizes the pectin

and causes it to “gel”

Ca2+ interacting

with pectin at tip

of pollen tube

Molecular gastronomists react

calcium with pectin-like polymers

to produce interesting foods

Ca2+

Pectin

© 2014 American Society of Plant Biologists

Calcium oscillations are mediated by

ion channels, pumps and carriers

Venkateshwaran, M., Cosme, A., Han, L., Banba, M., Satyshur, K.A., Schleiff, E., Parniske, M., Imaizumi-Anraku, H. and Ané, J.-M. (2012). The recent evolution of a symbiotic ion channel in the legume family altered

ion conductance and improved functionality in calcium signaling. Plant Cell. 24: 2528-2545. Evans, N.H. and Hetherington, A.M. (2001). Plant physiology: The ups and downs of guard cell signalling. Curr. Biol. 11:

R92-R94 with permission from Elsevier; Kudla, J., Batistič, O. and Hashimoto, K. (2010). Calcium signals: The lead currency of plant information processing. Plant Cell. 22: 541-563.

A model of the ionic fluxes that result in

calcium oscillations around the nucleus

during symbiotic interactions

Ca2+ oscillations contribute

to guard cell functions

How Ca2+

oscillations are

decoded remains

incompletely

resolved

© 2014 American Society of Plant Biologists

Summary: Calcium

• Much of a plant’s calcium may be in the form of calcium

oxalate crystals

• Free Ca2+ ion is mainly stored outside cytosol, in

apoplast and vacuole

• Calcium has a structural role in cell walls, particularly

pectin gelling

• Calcium has a signaling role conferred by transient

spikes in cytosol

© 2014 American Society of Plant Biologists

Macronutrients: Summary

• Macronutrients (N, P, K, S, Mg, Ca) are essential

elements that must be acquired from the environment

• Soil microbes affect nutrient availability and uptake

• Nutrient-specific transporters control uptake,

translocation and remobilization of mineral nutrients

• Some macronutrients are assimilated into organic

compounds

• Uptake and assimilation reactions are coordinated by

nutrient availability and demand

• Replenishment of soil nutrients is essential for high-

yielding agricultural systems

© 2014 American Society of Plant Biologists

Macronutrients - Summary

Diaz, R.J. and Rosenberg, R. (2008). Spreading Dead Zones and Consequences for Marine Ecosystems. Science. 321: 926-929.

The ecological impacts of agriculture are huge and

growing – most of these hypoxic regions arose

since 1950 and are attributed to human activities

© 2014 American Society of Plant Biologists

Gerland, P., Raftery, A.E., Ševčíková, H., Li, N., Gu, D., Spoorenberg, T., Alkema, L., Fosdick, B.K., Chunn, J., Lalic, N., Bay, G., Buettner, T.,

Heilig, G.K. and Wilmoth, J. (2014). World population stabilization unlikely this century. Science. 346: 234-237.

Macronutrients - Summary

9.6 billion

(2050)

7.2 billion

(2012)

10.9 billion

(2100)

WORLD POPULATION PROJECTION

Demand for food

will not slow down

during this century

We must find innovative

solutions to the challenge of

feeding the plants that feed us

© 2014 American Society of Plant Biologists

Ongoing research: Learn how plants

integrate different nutrient needs

Kellermeier, F., Armengaud, P., Seditas, T.J., Danku, J., Salt, D.E. and Amtmann, A. (2014). Analysis of the root system architecture of Arabidopsis provides a quantitative readout of crosstalk between nutritional signals.

Plant Cell. 26: 1480-1496. White, P.J., George, T.S., Dupuy, L.X., Karley, A.J., Valentine, T.A., Wiesel, L. and Wishart, J. (2013). Root traits for infertile soils. Front. Plant Sci. 4: 19.

How do roots optimize

growth when two or more

nutrients are limiting?

Cluster analysis of root

traits that enhance

acquisition of various

nutrients

Interactive effects

of nutrients and

daylength on root

growth

How can understanding

this integration support

breeding efforts?

© 2014 American Society of Plant Biologists

Ongoing research: Use best

practices for nutrient management

International Plant Nutrition Institute; See also American Society of Agronomy; Video link Plant Nutrition Institute

Manage nutrients

properly, using

the “4Rs”

Right Right

Right Right

NH4NO3 or

Urea?

How much?

Between rows? On

surface or deep?

Before planting?

During vegetative

growth phase?

Continue to develop technologies

to ensure optimal fertilizer use,

and make them affordable