Cell/Development/Systems

Abstract

C-5-5 - Brassinosteroids modulate meristem fate and differentiation of unique inflorescence morphology in Setaria viridis

Sunday, July 15
2:23 PM - 2:43 PM

Inflorescence architecture is a key determinant of yield potential in cereal crops and is patterned by placement and developmental fate of axillary meristems. In grasses, flowers and grain are borne from spikelets, which differentiate in the final iteration of axillary meristem branching. In Setaria spp., inflorescence branches terminate in either a spikelet or a sterile “bristle”, and these structures appear to be paired. In this work, we leverage Setaria viridis to investigate a novel role for brassinosteroids (BRs), a class of phytohormones, in specifying bristle identity and maintaining spikelet meristem determinacy. We report the cloning and characterization of the bristleless 1 (bsl1) locus in Setaria, which encodes a rate-limiting enzyme in BR biosynthesis. Loss-of-function bsl1 mutants fail to initiate a bristle identity program, resulting in homeotic conversion of bristles to spikelets. In addition, spikelet meristem determinacy is altered in the mutants, which produce two florets per spikelet instead of one. Both of these phenotypes provide avenues for enhanced grain production in cereal crops. Our results indicate that the spatiotemporal restriction of BR biosynthesis at boundary domains influences meristem fate decisions during inflorescence development, and this is partly through regulation of meristem identity genes that are conserved across grasses. Generation of mutant alleles in the maize ortholog of bsl1, ZmD11, indicates conserved function in panicoid cereals. Genetic crosses with known maize developmental mutants are being carried out to place bsl1/ZmD11 in a genetic framework and to further investigate the molecular mechanisms linking BR biosynthesis to meristem fate. Characterization of bsl1 gene function across grasses provides novel insight into the molecular basis underlying morphological variation in inflorescence architecture.


 

Co-Authors

Jiani Yang – Donald Danforth Plant Science Center; Adriana Chepote – Donald Danforth Plant Science Center; Shuiyi Thames – Donald Danforth Plant Science Center; Hui Jiang – Donald Danforth Plant Science Center; Norman Best – Purdue University; Brian Dilkes – Purdue University

Andrea Eveland

Donald Danforth Plant Science Center

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C-5-5 - Brassinosteroids modulate meristem fate and differentiation of unique inflorescence morphology in Setaria viridis



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