Cryptochrome-mediated blue light regulates cell lignification via PbbHLH195 activation of the PbNSC in pear fruits.

The presence of stone cells in pear fruit, caused by lignified secondary cell walls (SCWs), leads to a grainy texture in the fruit flesh, thereby compromising its overall quality. Lignification is influenced by various environmental signals, including light, however the underlying mechanism are poorly understood. This study reveals that SCW thickening and lignin accumulation in stone cells were regulated by a blue light signal, mediated through the activation of PbNSC by PbbHLH195. The results revealed that the stone cell formation was prompted by supplementary with blue light, with lignin accumulation linked to the upregulation of the NAC STONE CELL PROMOTING FACTOR (PbNSC). PbbHLH195 was identified as a novel molecular hub connecting lignification to blue light signal through its physical interaction with PbCRY1a. The biochemical and functional analysis indicates that PbbHLH195 contributes to stone cell lignification by activating the promoter of PbNSC. Our findings offer novel insights into the mechanisms of lignin biosynthesis in response to blue light, identifying valuable genetic targets for enhancing the fruit quality of pear.