Can plant survive without steroids: Modulation of plant architecture and sex determination through brassinosteroid biosynthesis and signaling

Shoot architecture is a key determinant of grain yield in maize. Among the major plant growth regulators, brassinosteroids (BRs) affect multiple developmental processes and plant architecture traits, including organ size, sex determination, and leaf angle. However, genetic mechanisms by which BRs regulate plant architecture traits in maize remain poorly understood. We have generated and characterized several brassinosteroid biosynthesis and signaling mutants that emphasize the role of BRs in plant growth and development. Two of BR synthetic mutants include brassinosteroid deficient semi-dwarf (bds1) and bds2. The bds1 mutant is a point-nonsense EMS-induced mutation we localized to a gene that encodes an enzyme likely involved in BR biosynthesis. Using phylogenetic and sequence similarity analysis, we identified a bds1 close homolog, bds2 and generated several mutant alleles by remobilizing a nearby Ds transposable element. Contrary to bds1 mutants, the bds2 single mutants were indistinguishable from wild-type plants. However, the bds1-R; bds2-Ds double mutants exhibited enhanced bds1 developmental defects such as plant dwarfness and tassel feminization. Based on these results, we propose that bds1 and bds2 cooperatively regulate shoot architecture and BR biosynthesis. Cabbage (cbg1 and cbg2) are another pair of BR biosynthetic mutants that we identified using Mutator transposons and characterized. Neither single (cbg1 and cbg2) mutant displayed obvious developmental defects. However, their double-mutants (cbg1;cbg2) had extreme defects such extreme dwarf stature, smaller leaves, fewer tassel branches and reduced root growth. Thus, we hypothesize that cbg1 and cbg2 redundantly function plant growth and development via BR biosynthesis.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

dissertation

Discipline thesis:degree_discipline

Genetics

Department dc:contributor.department

Department of Genetics, Development, and Cell Biology (LAS)

Grantor

Iowa State University

Year dc:date.issued

2024

Author dc:creator

• Zebosi, Brian

Advisors dc:contributor.advisor

• Vollbrecht, Erik
• Hufford, Matthew B
• Yin, Yanhai
• Becraft, Philip W.
• Lübberstedt, Thomas

Language dc:language.iso

en

DOI

https://doi.org/10.31274/td-20250502-270

OAI identifier oai:identifier

oai:dr.lib.iastate.edu:20.500.12876/8zn7D6Xw