Analysis of CsPAP-fib regulation of cucumber female differentiation in response to low night temperature conditions

In this study, the expression pattern of CsPAP-fib under different night temperature conditions (12 °C, 18 °C, and 24 °C) was analyzed using qRT-PCR, the subcellular localization of CsPAP-fib protein was determined, and sense and antisense CsPAP-fib were transformed into cucumber. The first node with female flowers and the female flower rate were calculated and recorded. Next, the ethylene and gibberellin contents were determined. The expression of CsPAP-fib in cucumber leaves was the highest under the low night temperature (12 °C) condition and was significantly higher than that in the roots, stems and shoot tips; however, under the high night temperature (24 °C) and normal night temperature (18 °C) conditions, no significant differences in CsPAP-fib expression in the roots, stems, leaves, shoot tips and other organs were observed. The expression of CsPAP-fib was the highest in cucumber leaves during the two-leaf stage and was significantly higher than that during the four-leaf stage. CsPAP-fib played a functional role mainly in chloroplasts. The overexpression of CsPAP-fib significantly improved the rate of cucumber female flowering and reduced the first node with a female flower. Thus, CsPAP-fib is a relevant gene for the regulation of cucumber female differentiation under low night temperature conditions. Altogether, CsPAP-fib is induced by a low night temperature (12 °C) and promotes the formation of cucumber femaleness by increasing the female flowering rate and decreasing the first node with a female flower. CsPAP-fib may be a relevant gene for cucumber femaleness differentiation at a low night temperature.