Seed storage protein gene regulation—A jig-saw puzzle

Abstract

Seed storage proteins are synthesized in high abundance during seed development and maturation, and are characterized as mid-embryogenesis and late-embryogenesis abundant proteins. The regulation of transcription of seed-protein gene families is not coordinated and transcription of each gene family is independently regulated. All seed protein gene families are regulated, in part, at the transcriptional level and a number of <i>cis</i>-acting elements and <i>trans</i>-acting factors are involved in this regulation. In many cases, a combinatorial interaction among transcription factors plays a critical role. In addition, CpG methylation has been found to be responsible for maintenance of the seed protein genes in an inactive state in tissues other than developing seeds. In some cases, a type of post-transcriptional control has been reported. In these cases, even when the transcription rates of seed protein and non-seed protein genes are similar, their mRNA levels vary upto 10000-fold. Formation of hairpin-loop structure in <i>zein</i> mRNA has been reported to serve as a kind of translational control. Proteins like Hsp70/Bip have been reported to play a critical role in the developing endosperm. This review highlights the regulation of seed storage protein genes at various levels with a view to understand the biological mechanisms regulating their synthesis.