The maize tasselseed4 microRNA controls sex determination and meristem cell fate by targeting Tasselseed6/indeterminate spikelet1

Abstract

In maize (Zea mays), sex determination occurs through abortion of female carpels in the tassel and arrest of male stamens in the ear. The Tasselseed6 (Ts6) and tasselseed4 (ts4) mutations permit carpel development in the tassel while increasing meristem branching, showing that sex determination and acquisition of meristem fate share a common pathway. We show that ts4 encodes a mir172 microRNA that targets APETALA2 floral homeotic transcription factors. Three lines of evidence suggest that indeterminate spikelet1 (ids1), an APETALA2 gene required for spikelet meristem determinacy, is a key target of ts4. First, loss of ids1 suppresses the ts4 sex determination and branching defects. Second, Ts6 mutants phenocopy ts4 and possess mutations in the microRNA binding site of ids1. Finally, IDS1 protein is expressed more broadly in ts4 mutants compared to wild type. Our results demonstrate that sexual identity in maize is acquired by limiting floral growth through negative regulation of the floral homeotic pathway.

Maize (Zea mays): A Model Organism for Basic and Applied Research in Plant Biology

“…In maize, sexual identity is acquired through the programmed cell death of stamen primordia in female flowers and the corollary abortion of carpel primordia in male florets (Cheng et al 1983). The developmental partitioning of male and female flowers has implications for the discovery of genes controlling sex determination in maize (Delong et al 1993;Chuck et al 2007Chuck et al , 2008. Moreover, this physical separation of male and female flowers greatly facilitates controlled pollinations, in that ear and tassel shoots can be easily covered to prevent pollen contamination and to collect pollen, respectively.…”

Disruption of OPR7 and OPR8 Reveals the Versatile Functions of Jasmonic Acid in Maize Development and Defense

“…Exogenous application of JA into the whorl of opr7 opr8 reversed the feminized tassel into a normal male tassel ( Figure 3A), confirming that JA is required for male inflorescence development. Six ts maize mutants have been well characterized, and the genes responsible for four of them, ts1 (Acosta et al, 2009), ts2 (DeLong et al, 1993 ts4 (Chuck et al, 2007), and ts6 (Chuck et al, 2007), have been cloned. Showing JA deficiency is responsible for the tasselseed phenotype, our results are in accordance with the recent report that ts1 is due to a mutation of a JA-producing lipoxygenase (Acosta et al, 2009).…”

The obscure events contributing to the evolution of an incipient sex chromosome in Populus: a retrospective working hypothesis

“…Moreover, recent studies investigating genes that control sex determination in maize reveals that a miRNA is involved in the determination of the male inflorescence (Banks 2008). Here, the tasselseed4 miRNA, i.e., miR172, targets APE-TALA2 floral homeotic transcription factors (Chuck et al 2007). miR172 also targets F-box family protein (FKF1) in Arabidopsis, and in Eschscholzia californica, miR172 appears to control protein degradation and sex determination (Barakat et al 2007b).…”