SnRK2.6 phosphorylates sucrose transporter ZmSUT1 to enhance yield by modulating leaf senescence in maize.

Abstract

The extended stay-green trait is beneficial to increase photosynthetic efficiency, thereby enhancing crop yield. However, factors and mechanisms affecting this process remain largely unknown. Here, we cloned a leaf precocious senescence gene (<i>lps1-1</i>) and created additional null alleles. All <i>lps1</i> mutants exhibited accelerated leaf senescence with reduced chlorophyll contents and photosynthetic efficiency. The 100-kernel weight and storage reserve content were decreased in <i>lps1</i> kernels, while the opposite was observed in overexpression lines. <i>Lps1</i> encoded a protein kinase SnRK2.6 that phosphorylated the sucrose transporter ZmSUT1 in the BETL region, thereby enhancing protein stability, homodimer formation ability, and sucrose transport activity. Overexpression of <i>ZmSUT1</i> delayed leaf senescence and enhanced photosynthetic capacity and kernel weight, while mutation of <i>ZmSUT1</i> did the opposite. This mechanism appears to be conserved in grasses. Our findings provide insights for yield and quality improvement in crops through delaying leaf senescence.