Poster: Reproductive Development

Abs # 482: Invertase Expression Responds to VP1-mediated ABA Signals During Early Kernel Development

Presenter:	Eveland, Andrea L, aeveland@ufl.edu
Authors	Eveland, Andrea L (A) (B)  Huang, Li-Fen  (A) (B)  Avigne, Wayne T (A) (B)  Koch, Karen E (A) (B)
Affiliations:	(A): University of Florida (B): Program in Plant Molecular & Cellular Biology

Sucrose cleavage by invertase generates hexoses essential for growth and sugar signaling during development of maize kernels. Expression of vacuolar invertase predominates in expanding maternal tissues of young kernels whereas that of filial cell wall invertase is enhanced during later stages of development. The purpose of this study is to test the influence of ABA-signaling on developmental patterns of gene regulation for vacuolar and cell wall invertases by comparing wild-type (WT) and vp1 kernels, as well as localized expression in embryo and endosperm. The vp1 mutants are insensitive to ABA and therefore germinate precociously on the ear, providing an ideal model for study of ABA-responsive gene expression during development. Invertase expression in young kernels was quantified via a sensitive real-time PCR approach. Under greenhouse conditions, a vacuolar acid invertase, Ivr2A, was expressed very early in the development of pollinated kernels, with mRNA levels peaking at 4 DAP and dropping sharply below detectable levels after 6 DAP. In plants mutant for the VP1 gene, Ivr2A expression appeared to peak at 2 DAP and descended slowly, remaining detectable into later developmental stages. The expression pattern for VP1 may be responding to ABA in the maternal tissue prior to pollination, which is consistent with the profile of Ivr2A expression in ABA insensitive mutants. The difference in invertase expression between WT and vp1 kernels provides evidence for a role of ABA-signaling in crosstalk with sugar sensing during seed development. Understanding the interactions between invertase-mediated sugar signaling and hormones affecting gene regulation in early kernels may provide invaluable insights into mechanisms underlying grain development.