Expression of a novel PSK-encoding gene from soybean improves seed growth and yield in transgenic plants

摘要

Main conclusionExpression ofGmPSK1, a novel PSK-encoding gene from soybean, increases seed size and yield in transgenic plants by promoting cell expansion.Phytosulfokine- (PSK-), a sulfated pentapeptide hormone with the sequence YIYTQ, plays important roles in many aspects of plant growth and development. In this study, we identified a pair of putative precursor genes in soybean, GmPSK1 and -2, encoding a PSK-like peptide: PSK-. Similar to PSK- in amino acid composition, the sequence of PSK- is YVYTQ, and the tyrosines undergo sulfonylation. Treatment of Arabidopsis seedlings with synthetic sulfated PSK- significantly enhanced root elongation, indicating that PSK- might be a functional analog of PSK-. Expression pattern analysis revealed that the two GmPSK genes, especially GmPSK1, are primarily expressed in developing soybean seeds. Heterologous expression of GmPSK1 under the control of a seed-specific promoter markedly increased seed size and weight in Arabidopsis, and this promoting effect of PSK- on seed growth was further confirmed in transgenic tobacco constitutively expressing GmPSK1. Cytological analysis of transgenic Arabidopsis seeds revealed that PSK- promotes seed growth by inducing embryo cell expansion. In addition, expression analysis of downstream candidate genes suggested that PSK- signaling might regulate cell wall loosening to promote cell expansion in Arabidopsis seeds. Overall, our results shed light on the mechanism by which PSK- promotes seed growth, paving the way for the use of this new peptide for biotechnological improvement of crop seed/grain size and yield.