SHB1 regulates seed development in Arabidopsis

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

PI: Min Ni Proposal number: IOS-0919886 Proposal Title: "SHB1 regulates seed development in Arabidopsis" Double fertilization in angiosperms leads to the formation of a diploid embryo and a triploid endosperm. In Arabidopsis, seed development undergoes an initial phase of active endosperm proliferation followed by a second phase in which embryo grows rapidly at the expense of the endosperm. Since mature seed size is largely attained during the initial phase, seed size is coordinately regulated by the growth of the maternal ovule, the endosperm, and the embryo. The mechanisms underlying seed size control are still not well understood, yet seeds form the bulk of the diet of human population. The gene SHB1 is a positive regulator of Arabidopsis seed development that operates through regulation of both cell size and cell number. shb1-D, a gain-of-function allele, increases seed size and shb1, a loss-of-function allele, reduces seed size. The increase in seed size of shb1-D is associated with the timing of endosperm cellularization, enlargement of chalazal endosperm, and subsequent embryo development. SHB1 regulates the expression of the genes MINI3 and IKU2, which encode a WRKY transcription factor and an LRR receptor kinase respectively. SHB1 associates with MINI3 and IKU2 promoters in vivo, and directly interacts with MINI3. The goal of this project is to test if SHB1 is recruited as a co-activator by a WRKY transcription factor to control gene expression required for endosperm development. Various cellular, biochemical, and molecular approaches will be used to investigate the interaction of SHB1 with MINI3 and the biological consequence of SHB1-MINI3 interaction. Understanding the mechanisms of seed size regulation has the potential to generate a potential increase in seed yield and a concomitant increase in the amount of protein and oil produced per seed. This project will provide excellent opportunities for undergraduates, graduate students, and postdoctoral fellows to gain significant research experiences, and most importantly, to develop their ability to critically analyze and solve scientific problems. Seed size is a yield trait that traditional plant breeding has limited success in improving. Seed development in major seed crops such as soybean and canola follows a very similar path to Arabidopsis. Enhancing the potential for large seed size represents one of the most promising and least explored avenues for generating a significant increase in agricultural yield.