Analysis of opaque2 transcription system for regulation of zein protein expression

Abstract

Quality Protein Maize (QPM), rich in lysine and tryptophan has prospects for human health and higher farmer remuneration. Maize opaque mutants have been used to develop current quality protein varieties. Many rounds of breeding efforts are required for sufficient endosperm modification to improve protein and grain quality simultaneously. This is because while the amount of lysine and tryptophan increases, the maize grain texture is adversely affected. This makes the grain prone to post-harvest loses. Zein proteins are responsible for grain hardness. However, they are poor in lysine and tryptophan content, and are primarily responsible for low nutritional value of maize grain. Precision genome editing can be used to accelerate improvement of nutritional quality in local germplasm, without detrimental effects on grain quality. A computational model of opaque2 basic leucine zipper domain interacting with its cognate DNA sequence 5' GATGACGTGA 3' was prepared. Amino acid residues in the o2 transcription factor protein that interact with nucleobases in DNA have been deciphered. Such interacting residues are potential targets for gene editing of o2 protein to regulate transcription of zein proteins. Since many types and isoforms of zeins are present in maize germplasm, engineering of o2 transcription factor will affect all the genes it regulates. On the other hand, specific type and/or isoform of zeins can be targeted if the promoter regions is engineered, instead. The present work describes analysis of interaction of amino acids with nucleobases in the target sequence