DEHYDRIN GENE-EXPRESSION IN NORMAL AND VIVIPAROUS EMBRYOS OF ZEA-MAYSDURING SEED DEVELOPMENT AND GERMINATION

Dehydrins are a group of hydrophilic proteins whose proposed function is to protect plant cells from damage caused by dehydration and rehydr ation. Expression of the dehydrin gene (dhn) in vegetative tissues of cereal crops and other plants can be induced by both water stress and by the phytohormone, abscisic acid (ABA). In this work, dhn expression was studied with Zea mays during embryogenesis and seed germination i n normal and several viviparous mutants (vp1, vp5, vp7, vp8, and vp9), in which ABA biosynthesis is defective. All normal embryos were obser ved to have initiated dhn transcription by 22 days after pollination ( DAP), and continued to accumulate transcripts throughout seed developm ent. The vp mutant embryos contained significantly lower levels of ste ady state dhn transcripts. Linear correlation between dhn transcript l evels and endogenous ABA content was significant (p < 0.001) for both normal (r = 0.71) and the vp mutants (r = 0.89). Experiments with exci sed embryos at different developmental stages support the role of ABA regulation of dhn expression, as ABA treatment resulted in the accumul ation of dhn transcripts during culture of immature and mature embryos regardless of developmental stage and genetic background.