Downstream of GA4, PbCYP78A6 Regulates Parthenogenesis by Mediating Cell Cycle-Related Genes in Pear (Pyrus Bretshneider Rehd.)

Abstract Background: Parthenocarpy results in traits attractive to both consumers and breeders, and it overcomes the obstacle of self-incompatibility in the fruit set of horticultural crops, including pear (Pyrus bretshneider). However, there is limited knowledge regarding the genetic and molecular mechanisms that regulate parthenogenesis. Results: Here, in a transcriptional comparison between pollination-dependent and GA4-induced parthenocarpy, PbCYP78A6 was identified and proposed as a candidate gene involved in parthenocarpy. PbCYP78A6 is similar to Arabidopsis thaliana CYP78A6 and is highly expressed in pear hypanthia. The increased PbCYP78A6 expression, as assessed by RT-qPCR, was induced by pollination and GA4 exposure. The ectopic overexpression of PbCYP78A6 contributed to parthenocarpic fruit production in tomato. The PbCYP78A6 expression coincided with fertilized and parthenocarpic fruitlet development and the expression of fruit development-related genes as assessed by cytological observations and RT-qPCR, respectively. PbCYP78A6 RNA interference and overexpression revealed that the gene is an upstream regulator of fruit development-related genes in pear. Conclusions: Our findings indicate that PbCYP78A6 plays a critical role in cell proliferation and provide insights into controlling parthenocarpy.