Expression of a novel PSK-encoding gene from soybean improves seed growth and yield in transgenic plants
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Expression of GmPSKγ1 , a novel PSK-encoding gene from soybean, increases seed size and yield in transgenic plants by promoting cell expansion.
Phytosulfokine-α (PSK-α), 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, GmPSKγ1 and -2, encoding a PSK-like peptide: PSK-γ. Similar to PSK-α in amino acid composition, the sequence of PSK-γ is YVYTQ, and the tyrosines undergo sulfonylation. Treatment of Arabidopsis seedlings with synthetic sulfated PSK-γ significantly enhanced root elongation, indicating that PSK-γ might be a functional analog of PSK-α. Expression pattern analysis revealed that the two GmPSKγ genes, especially GmPSKγ1, are primarily expressed in developing soybean seeds. Heterologous expression of GmPSKγ1 under the control of a seed-specific promoter markedly increased seed size and weight in Arabidopsis, and this promoting effect of PSK-γ on seed growth was further confirmed in transgenic tobacco constitutively expressing GmPSKγ1. Cytological analysis of transgenic Arabidopsis seeds revealed that PSK-γ promotes seed growth by inducing embryo cell expansion. In addition, expression analysis of downstream candidate genes suggested that PSK-γ signaling might regulate cell wall loosening to promote cell expansion in Arabidopsis seeds. Overall, our results shed light on the mechanism by which PSK-γ promotes seed growth, paving the way for the use of this new peptide for biotechnological improvement of crop seed/grain size and yield.
KeywordsArabidopsis Cell expansion Phytosulfokine PSK-γ Seed size Soybean
Days after pollination
This work was supported by the National Natural Science Foundation of China (31500197 and 31570241), the 973 National Key Basic Research Program in China (2015CB158300), and the Shanghai Key Program of Supporting Program (15230500100).
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Conflict of interest
The authors declare that they have no conflict of interest.
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