Poster: Reproductive development

Abs # 368: ABA Sensing Mediates Expression of Vacuolar Invertase During Female Reproductive Development in Maize

Presenter:	Eveland, Andrea L., aeveland@ufl.edu
Authors	Eveland, Andrea L. (A)   Avigne, Wayne T (A)   Karen, Koch E (A)
Affiliations:	(A): University Of Florida, Plant Molecular and Cellular Biology Program

Sucrose partitioning among maize floral tissues during the pre- and early post-pollination phases of reproductive development may be critical to the timing of female flower maturation. Sucrose cleavage by a vacuolar invertase, Ivr2A, provides hexoses essential for growth and expansion of sink tissues, and may be a key enzyme in the carefully-controlled, sequential expansion of maize flower tissues. To address this possibility, Ivr2A expression was measured over an early developmental series under field conditions using a sensitive Q-PCR approach. Data show that Ivr2A expression coincides with the rapid expansion of silk and floral tissue during the pre-pollination period, and transcript levels decline towards pollination. At this time, maximal mRNA abundance and probable hexose accumulation shifts to the ovary as flower parts senesce. This controlled pattern of expression may be significant to the timing of female floral development and consequently to silk emergence for optimal pollination. To test the possible involvement of ABA, we employed a vp1 mutant which germinates precociously due to ineffective ABA sensing. Analysis of this mutant showed that the careful control and timing of Ivr2A expression among floral organs was disrupted by a lack of endogenous ABA signaling in the vp1 mutant plants. VP1 may thus play a regulatory role in the fine tuning of Ivr2A expression during early reproductive development. Transcript levels of Ivr2A were more than two-fold greater in ovaries of vp1 mutants than those of wild type plants. These data show that an intact ABA sensing system is essential for maintaining a normal progression of Ivr2A vacuolar invertase expression within floral parts, subsequent tissue expansion, and thus optimal timing of female flowering.