Inadequate lysine content of wheat endosperm proteins - possibility of correcting it by CRISPR-Cas system of genome editing

Abstract

Proteins in endosperms of mature wheat seeds contain ~ 2.5% lysine. Proteins in endosperms of immature wheat seeds after 8 days of anthesis, interestingly contain ~ 8% lysine. Wheat endosperm proteins collected 15 days after anthesis, when treated with proteases isolated from endosperms 20 days after anthesis, released 10.2% lysine and 5.6% leucine. In contrast, the same proteins, when treated with proteases isolated from endosperms 8 days after anthesis, released 7.0% lysine and 12.0% leucine. The protease C, that could cleave polylysine, but could not cleave polyaspartic acid and polyglutamic acid, appeared only at 16 days after anthesis and continued to be present till 28 days after anthesis. Soybean trypsin inhibitor inhibited the activity of protease C completely. Transcriptome analysis of developing wheat seeds has revealed the presence of three major transcripts containing trypsin-like domains. The amounts of these three transcripts increased from 2 weeks after anthesis to 4 weeks after anthesis and decreased thereafter. If a wheat variety could be created which is devoid of protease C or the above mentioned trypsin like proteases, the lysine content of endosperm proteins of that variety would possibly be higher. This could today be achieved by using the CRISPR-Cas systems of genome editing.