Inflorescence development: the basis of maize...

Inflorescence development:

the basis of maize productivity

Paula McSteen

Division of Biological Sciences

Bond Life Sciences Center

University of Missouri-Columbia

Overview

Inflorescence development

Genetic analysis of inflorescence

development – the role of auxin

Hormonal and environmental control of

ear shoot formation

tassel =

male inflorescence

ear =

female inflorescence

McSteen et al 2000 TIPS 5: 61-66

Maize has separate male and

female inflorescences

spikelet pair

floret pair tassel

Tassel inflorescence

mature ear ear shoot

Ear inflorescence

root apical meristem

shoot apical meristem

axillary meristem

Meristems control development

Tsiantis and Hay 2003 Nature Reviews Genetics 4:169-180

Vegetative to floral transition

- leaves to flowers

McSteen et al 2000 TIPS 5: 61-66

Vegetative

meristem

Inflorescence

meristem

Transition

stage

Inflorescence meristem

Maize inflorescence development

– transition stage

X Wu and P McSteen, unpublished 0.5mm

IM


– branch meristem

1.0mm X Wu and P McSteen, unpublished

BM

spikelet pair meristem


- spikelet pair meristem


SPM


spikelet meristem


- spikelet meristem


SPM

SM


spikelet meristem


- second spikelet meristem

5.0mm S Barazesh and P McSteen, unpublished

SM

Spikelet pair meristem

Spikelet meristem


- apical meristem collapse

6.0mm K Phillips and P McSteen, unpublished


Spikelet meristem


- floral meristem

Floral meristem 8.5mm X Wu and P McSteen, unpublished

FM


Spikelet meristem

Floral meristem


- second floral meristem

11mm X Wu and P McSteen, unpublished

Tassel and ear – similar development

Tassel Ear Phillips et al 2011 Plant Cell, in press

IM

SPM

SM

BM

IM

SPM

SM

FM

Sex determination occurs later

adapted from Veit et al 1983 Plant Cell 5:1205-1215

Summary of development

BM, SPM, SM, FM = axillary meristems

Ear shoot, tiller bud = axillary meristems

Tassel and ear have similar development

Overview





ear shoot formation

Genetic analysis of inflorescence development

auxin biosynthesis – vanishing tassel2 (vt2)

auxin transport – barren inflorescence2 (bif2)

auxin response – barren stalk1 (ba1)

bif2 mutants make fewer branches

Normal bif2 McSteen et al 2001 Development 128:2881-2891

bif2 mutants make fewer kernels

Normal bif2

bif2 fails to produce axillary meristems

Normal bif2

SPM

IM

bif2 is required for initiation

of all axillary meristems

in maize

McSteen et al 2001 Development 128:2881-2891

McSteen et al 2007 Plant Physiology 144:1000-1011


bif2 encodes a serine/threonine

protein kinase

Model for BIF2 function

BIF2

P

Cell

membrane

Promoter BA1 targets

IAA

Nucleus

BIF2 P

P

BIF2 P

P

BA1 P

ZmPDK P

Auxin transport

Axillary meristem initiation

Skirpan et al 2008 Plant J 55:787-797

Skirpan et al 2009 Plant Cell Physiol 50:652-657

Genetic analysis of inflorescence development

auxin biosynthesis – vanishing tassel2 (vt2)

auxin transport – barren inflorescence2 (bif2)

auxin response – barren stalk1 (ba1)

vt2 affects inflorescence development

Normal vt2 vt2 Normal

Phillips et al 2011 Plant Cell in press

vt2 mutants fail to produce

axillary meristems

Normal vt2

AM

IM

SPM

IM

TRP

IAM IAOx IPA TAM

IAN IAAld HTAM

IAA

Four tryptophan-dependent auxin

biosynthesis pathways are proposed

spi1

vt2


Auxin is required for initiation

of all axillary meristems

in maize


Wu and McSteen 2007 Am J Bot 94: 1745-1755

Gallavotti et al 2008 PNAS 105:15196-15201

Skirpan et al 2009 Plant Cell Physiol 50:652-657


Overview





ear shoot formation

Hormonal and environmental control of ear shoot formation

initiation - auxin

outgrowth - hormones, density, fertilizer

maintenance - cytokinin, thiamine, boron

Auxin mutants have defects in

ear shoot initiation ear #

0

0.5

1

1.5

2

wt vt2

Ear

sh

oo

t N

um

ber

2.0

1.0

0.0

1.5

0.5

+/+ vt2/vt2


ba1 and ba2 mutants lack ear shoots

Normal ba2

Normal ba2

Skirpan and McSteen, unpublished

Normal ba1

Gallavotti et al 2004 Nature 432:630-635

N ba2


initiation - auxin



bud

root

shoot

leaf

IAA

s

trig

ol

CK

McSteen 2009 Plant Physiology 149:46-55

Hormonal factors

impacting bud outgrowth

Auxin regulates tillering in rice

Xu et al 2005 Plant Cell Physiol 46:1674-1681

wildtype rice OsPIN1 mutant

shade low R/FR

fertilizer

bud

density

root

shoot

leaf

IAA

s

trig

ol

CK

McSteen 2009 Plant Physiology 149:46-55

Environmental factors

impacting bud outgrowth

Kebrom and Brutnell 2007 J Exp Bot 58:3079-3089

Light regulates tiller production

in sorghum

phyB

mutant

wildtype

sorghum

tb1 regulates tillering in maize

Normal maize tb1 mutant Hubbard et al 2002 Genetics 162: 1927-1935


initiation - auxin



Thiamine deficiency results in defects

in apical meristem maintenance

Woodward et al 2010 Plant Cell 22:3305-3317

Conclusions

multiple hormonal and environmental

impacts on ear formation

important to know the stage affected to

understand the mechanisms involved

similar mechanisms of regulation of all

axillary structures

Acknowledgements

PSU lab

Andrea Skirpan

Solmaz Barazesh

Xianting Wu

Kim Phillips

MU lab

Hong Yao

Amanda Durbak

Laura Matera

Collaborators

Andrea Gallavotti, UCSD

Bob Schmidt, UCSD

Yunde Zhao, UCSD

Simon Malcomber, CSULB

David Jackson, CSHL

Jerry Cohen, U Minnesota

Mike Scanlon, Cornell

Funding

NSF – bif2, AuxinEvoDevo

USDA – spi1, vt2

Inflorescence development: the basis of maize...

Documents

Transcript of Inflorescence development: the basis of maize...