Tasselseed5 overexpresses a wound-inducible enzyme, ZmCYP94B1, that affects jasmonate catabolism, sex determination, and plant architecture in maize

China Lunde,Samuel Leiboff,Athen Kimberlin,Sarah Hake,Abraham J Koo

doi:10.1038/s42003-019-0354-1

Abstract

Maize is monecious, with separate male and female inflorescences. Maize flowers are initially bisexual but achieve separate sexual identities through organ arrest. Loss-of-function mutants in the jasmonic acid (JA) pathway have only female flowers due to failure to abort silks in the tassel. Tasselseed5 (Ts5) shares this phenotype but is dominant. Positional cloning and transcriptomics of tassels identified an ectopically expressed gene in the CYP94B subfamily, Ts5 (ZmCYP94B1). CYP94B enzymes are wound inducible and inactivate bioactive jasmonoyl-L-isoleucine (JA-Ile). Consistent with this result, tassels and wounded leaves of Ts5 mutants displayed lower JA and JA-lle precursors and higher 12OH-JA-lle product than the wild type. Furthermore, many wounding and jasmonate pathway genes were differentially expressed in Ts5 tassels. We propose that the Ts5 phenotype results from the interruption of JA signaling during sexual differentiation via the upregulation of ZmCYP94B1 and that its proper expression maintains maize monoecy.

Highlights

IntroductionWith separate male and female inflorescences. Maize flowers are initially bisexual but achieve separate sexual identities through organ arrest
Maize is monecious, with separate male and female inflorescences
Both ts[1] and ts[2] have a reduced plant height[8]. Another tasselseed mutant was created by knocking out the duplicated orthologs of OPR3, a major OPR (12-oxo-phytodienoic acid reductase) gene in Arabidopsis that acts in jasmonic acid (JA) biosynthesis[12,13]

Summary

Introduction

With separate male and female inflorescences. Maize flowers are initially bisexual but achieve separate sexual identities through organ arrest. One mechanism is genetic self-incompatibility, in which distinct alleles in the male pollen and female pistil are required for successful seed set[1] Another mechanism is physical separation, which involves the development of unisexual flowers. Maize produces separate staminate (male) and pistillate (female) inflorescences called the tassel and the ear, respectively. A large number of sex-determination mutants have been identified in maize, given the easy visibility of tasselseed mutants in which silks (pistils) and kernels (seeds) are found in the normally male tassel. Ts[1] encodes a lipoxygenase, called ZmLox[8], that acts in jasmonic acid (JA) biosynthesis[9,10], and ts[2] encodes a monocot-specific[3] short-chain alcohol dehydrogenase[11] Both ts[1] and ts[2] have a reduced plant height[8]. Many modes of regulation are necessary to keep hormone action balanced for proper sex determination[20]

Methods

Results

Conclusion