Transcriptome profiling reveals candidate genes associated with sex differentiation induced by night temperature in cucumber

The sex differentiation of cucumber directly affects cucumber fruit yield, and low night temperature (LT) promotes female flower differentiation. However, studies on the effects of LT on sex differentiation are scarce. To better understand this mechanism, we used transcriptomics to examine the expression patterns of genes related to female flower differentiation in the cucumber cultivar 'C09-123' under LT and high night temperature (HT). We identified a total of 1654 differentially expressed genes in response to LT. There were 1147 up-regulated genes and 507 down-regulated genes under LT compared with their expression under HT. Gene ontology (GO) analysis revealed that the differentially expressed genes were mainly involved in cellular process, metabolic process, response to stimulus process and other processes (biological process). Many of these differentially expressed genes (DEGs) were related to glucose metabolism, cysteine and methionine metabolism and the ethylene and auxin signal transduction pathway and were up-regulated under LT, which promotes female differentiation, compared with their expression level under HT. These results suggest that changes in these genes are likely to affect the corresponding metabolism, thus inducing the female flower differentiation of cucumber under LT. Ethylene and auxin play important roles in the induction of female flower differentiation under LT. This study provides valuable resources for further exploring the molecular basis of LT induction of female flower differentiation and for enabling targeted breeding strategies for developing varieties with superior strong female differentiation to achieve yield potential.