Abstract

Auxin Evo-Devo: Genetic and Genomic Approaches to Understanding the Role of Auxin in Shoot Development

Auxin regulates nearly every aspect of plant growth and development. A better understanding of auxin’s function is therefore fundamentally important to basic plant biology and crop improvement. Previous research has demonstrated both conservation and diversification of auxin’s role in maize and Arabidopsis. This project will further our understanding of how auxin regulates shoot development, emphasizing maize shoot organogenesis. To identify additional genes functioning in auxin-mediated organogenesis, we are characterizing 147 maize mutants with distinctive vegetative and reproductive developmental defects. Together with previously characterized mutants, we have mapped 71 mutants to 40 locations in the maize genome. Eight of these loci had been cloned previously, and an additional six genes have been cloned on this project. Many of these genes encode proteins required for auxin biosynthesis, transport, and response. Preliminary phylogenetic analyses of 15 gene families have illustrated complex relationships amongst monocot and eudicot clades. Reverse genetic efforts guided by these phylogenetic relationships have confirmed 18 insertions in 12 genes. Further phylogenetic, functional and comparative expression analyses will test the conservation and diversification of auxin action mechanisms in all flowering plants.

Arabidopsis Maize Protein Function

taa1 vanishing tassel 2 (vt2)Tryptophan amino-

transferaseAuxin biosynthesis

yucca (yuc)sparse inflorescence1

(spi1)Flavin mono-oxygenase Auxin biosynthesis

pinformed1 (pin1) ZmPIN1a,b,c Auxin efflux carrier Auxin Transport

pinoid (pid) barren inflorescence2 (bif2)Serine threonine protein

kinaseAuxin Transport

naked pins in yucca (npy)

ZmNPY BTB-POZ-NPH3 Auxin signaling?

monopteros (mp) Zmmp2/10 Auxin Response Factor Auxin signal transduction

Aux/IAA ZmAux/IAAAux/IAA transcription

factorAuxin signal transduction

topless (tpl) ramosa enhancer2 (rel2)Transcriptional co-

repressorAuxin signal transduction

Rox1 barren stalk1 (ba1)bHLH transcription

factorAuxin response

? barren stalk2 (ba2)Protein interaction

domainAuxin response

nip5;1 tassel-less1 (tls1) Major intrinsic protein Membrane transport

bor1 rotten ear1 (rte1) Efflux transporter Membrane transport

thi1 tassel-less3 (tls3) Thiazole biosynthesis Thiamine biosynthesis

Mutants with a pin phenotype in Arabidopsis and a barren phenotype in maize

Arabidopsis Maize

AcknowledgementsWe thank Gerry Neuffer and the Maize Inflorescence Project for generating the mutants, the Maize Coop for providing the seed, Lu Gao, Mitzi Wilkening and Pat Schnable at Iowa State University for Sequenom analysis. This research was supported by the National Science Foundation grant number IOS 0820729/1114484.

Auxin is essential for shoot development

Jacob R. Withee1, Paula C. McSteen1, Simon T. Malcomber2, Andrea Gallavotti3, Yunde Zhao4, Naomi Altman5, Reka Albert6

1 Division of Biological Sciences, University of Missouri. Columbia, MO 65211. 2 Department of Biological Sciences, California State University. Long Beach, CA, 90840. 3 The Waksman Institute of Microbiology, Rutgers University. Piscataway, NJ 08854. 4 Section of Cell and Developmental Biology, University of California, San Diego. La Jolla, CA 92093. 5 Department of Statistics, The Pennsylvania State University. University Park, PA 16802. 6 Department of Physics, The Pennsylvania State University. University Park, PA 16802.

Reverse genetics: Confirmed Mu insertions

• Relative, qualitative gene expression for maize vt2 gene family determined from in silico analysis

• The vt2 and TAA1 clades are broadly expressed• Duplicate genes are expressed at a lower level• ZmTAR1/OsTAR1 clade is endosperm and seed specific

TAR1TAA1

TAR2

TAR3

vt2

ZmTAR1

ZmTAR1 dup

vt2 dup

TAR4

OsTAR1

ZmTAR3 ZmTAR4

vt2

du

p

Zm

TA

R1

du

p

spi d

up

yuc1

0/1

1

bif2

du

p

bif2

pa

ralo

g

bif2

pa

ralo

g

Zm

PIN

1a

mp

2

mp

10

Au

xIA

A

NP

Y1

a0

1

2

3

Functional genomics of maize barren mutants

• Genetic analysis of 147 EMS-induced barren mutants (in progress)• Mapped mutants using Sequenom MassArray SNP detection (71 completed, 22 in progress)• Allelism test and sequence (in progress, 15 confirmed or cloned)• Map-based cloning of 10-15 mutants (6 cloned, 12 in progress)

Map location of 40 barren* mutants in maize (blue have been cloned, dark blue cloned on this project)

ba2Ba-ub*

blast

1 2 3 4 5 6 7 8 9 10

rte1

kn1

Bif3

ba2

lg2Baub*

Dvd1

Bif1

baf1rel2

ba1

tls1

bif2

spi1

tls3

br-ub

bif*

Bif4

br*

tls2

bl*

te1

bif*

tls6

tls4

bl*

dw*

vt*

smp*

ub*

bl*

smp*

bif*

tls5

tls3

bif*

br-ub*

Mutants being cloned

vanishing tassel 2 (vt2) phylogeny and gene expression patterns

OsTAR2

OsTAR3OsTAR4

Coleoptile or Hypocot

yl

Root

Seedlin

g

SAM/Veg

. Meristem

Internode/

Stem

Immatur

e Leaves

Mature Leaves

Inflorescenc

e Meristem

Panicle/ Inflorescenc

e

Flower

s

Tassel

Anthers or

Floral

Organs

Ear

Silks/

Stigma

Husk

LeafFruit

Seed

Endosperm

Embryo

                             

                             

                     

                             

                               

                       

                       

                       

                                          

                                                                                                        

 

 

 

 

 

 

Highly expressed

Not expressed

bif*

an1

tls7

bl*ba*

vt2

vt2 spi1 bif2 PIN ARF1 AUX/IAA

NPY

Auxin Biosynthesis Auxin Transport Auxin Signal Transduction