Characterizing Auxin Biosynthetic Mutants in Arabidopsis thaliana

Nicole Colón CarriónDirection: Linda RoblesAlonso-Stepanova Lab

CHARACTERIZING AUXIN BIOSYNTHETIC MUTANTS IN ARABIDOPSIS THALIANA

Objective

This study aims to shed light on the auxin biosynthetic pathway by identifying genes involved in the pathway using a novel screen in Arabidopsis.

Auxin• Auxin biosynthesis can occur via tryptophan dependent or independent pathways• There are many unknowns in the auxin biosynthetic pathway and we hope to find regulating factors

● TAA1 gene encodes an aminotransferase that is used to convert TRP into IPA.

Ethylene : Induce Auxin synthesis

Ethylene

Col wei8

wei8 tar2

Col-O

Air Ethylene Figure 1. Represent the

effect of the lost of the aminotransferase

Enhancer screen for auxin biosynthetic mutants~50,000 wei8 DR5:GFP plants have been EMS mutagenized.

~100,000 plants have been screened.

~2100 “putants” have been picked.

Retesting of putants has been completed.

~ 200 have the loss of apical hook.

Of these, ~25 have a longer root.

Further characterization

Goal: To find other factors

contributing to auxin biosynthesis.

F2’s from crosses were analyzed at two timepoints for auxin sensitivity and ethylene

responses.

The recombination frequency was calculated.Recombination freq = total no of mutants/ total of offsprings X 100%

Root degeneration and DR5:GFP expression were monitored. Seedlings with the mutant phenotype were propagated for mapping.

Seedlings with the parental phenotype were selected for further analysis.

Mutants

18-40 Semi- dominant22-25-4 Recessive mutant21-44-5 Dominant12-20-2 Recessive mutant12-8-3 Recessive mutant2-93 Recessive mutant

Characterization of 2-93 at 3 days old

Ethylene media

Auxin media

Standard media

Col wei8 wei8 tar2 2-93

AT10 days

old

IAA10 days

old

ATDR5:GF

P10 days

old

IAADR5:GF

P10 days

old

2-93Col wei8

Characterization of 2-93 at 10 days oldwei8 tar2

F2’s for 2-93 cross

Cross Long root Total Ratio

Col 3 100 ~1:16

Ler 4 105 ~1:16

wei8 8 98 ~1:4

xCol x Ler x W8-1

0%2%4%6%8%

*2-93

*2-93

Results:2-93 mutant cross to Col and to Ler presented a 1:16 ratio, while the cross to wei8 presented 1:4 ratio meaning that it is a recessive mutation.

Chromosomal location of causal mutation in the 2-93 line

Acknowledgements• Dr. Alonso• Dr. Stepanova• Dr. Linda Robles• Dr. Sue Carson• Dr. Karen Merchante• Jeonga Yun• Dr. Nelson

Questions

THANKS FOR YOUR ATTENTION