The AtbZIP44 protein regulates the expression of a gene implicated in the loosening of the seed covering layers upon seed germination

Identification of a regulatory protein highly relevant in the process of loosening seed covering layers upon germination.

Seeds are the most important world crops, mainly those of cereals such are wheat, corn, rice and barley. The global seed market has grown rapidly in recent years and is currently worth around US $50 billion per year. However, high amounts of its production are lost due to the precocious germination in the mother plant (viviparism). In this context, a better understanding of the molecular networks that control seed dormancy and germination is crucial for improving seed quality, and increasing crop yield under variable environmental conditions.

In this work published in The Plant Journal, Prof. Pilar Carbonero´s group demonstrates that the AtbZIP44 transcription factor protein participates in the complex network that regulates germination, by positively affecting AtMAN7 gene expression; this gene encodes an endo-β-mananase (MAN; EC. 3.2.1.78) that facilitates the loosening of the seed covering layers during germination of the model plant Arabidopsis thaliana. The bioinformatic analysis of the promoter sequences of orthologous genes of AtMAN7 in several species of the Brassicaceae family (phylogenomics) discovered highly conserved motives. These conserved motives were used as baits in a yeast 1-hybrid screening of an arrayed yeast library of circa 1,200 TFs from A. thaliana. AtbZIP44 was identified as a putative regulator of the AtMAN7 expression and later validated by several molecular and physiological techniques. Co-expression in the micropylar endosperm of the putative regulator gene (AtbZIP44) and the regulated one (AtMAN7) was corroborated by microscopic techniques (see Figure).