Abstract

Tao Shutian College of Horticulture, Nanjing Agricultural University, Nanjing 211800, China The formation of stone cells is an important factor restricting the improvement of pear fruit quality, and the lignification process of cells is affected by light environment signals. Studies have shown that cryptochrome plays a pivotal role in promoting the formation of stone cells in response to environmental blue light signals, and affects the lignification process, but the pathway and molecular mechanism of light signaling in the lignification process are still unclear. In previous studies, the authors found that multiple lignin synthesis-related genes and transcription factors were induced to be highly expressed in the blue light environment, including the switch PbNSC of stone cell development. Based on yeast monohybrid library screening, the authors found that PbbHLH195, a key gene induced by blue light signal that acts upstream of PbNSC, and further combined with yeast monohybridization, luciferase experiments and EMSA experiments, it was found that PbbHLH195 can directly bind to the G-box element of the PbNSC promoter and activate its activity. Further analysis showed that the lignification process induced by blue light partly depended on PbbHLH195, and PbbHLH195 could directly interact with and be regulated by cryptochrome PbCRY1a, so PbbHLH195 was identified as a novel molecular hub connecting lignification and blue light signal. Biochemical and functional analysis showed that PbbHLH195 was involved in the lignification of stone cells by activating the PbNSC promoter, regulating downstream metabolic processes. The results of this study revealed the biological function of CRY1a for the first time in pears, constructed a molecular network centered on PbCRY1a, and constructed a molecular network centered on PbCRY1a, which expanded the role of cryptochrome in the secondary metabolism of pears, provided important theoretical basis and practical guidance for fruit quality improvement, and provided new insights into the biosynthesis mechanism of lignin under blue light.