First fruit inhibition and CRISPR-Cas9 inactivation of candidate genes to study the control of cucumber fruit set

Cucurbits represent an attractive model to explore the dynamics of fruit set. A fertilized ovary integrates signals from distant plant parts and “decides” whether to set fruit, or remain inhibited and later abort, with important implications to fruit yield. We set to characterize first fruit inhibition (FFI), i.e., the inhibitory effect of the first fruit on subsequent development of younger ovaries. The effect was physiologically studied and quantified, and we compared its strength and persistence in pollinated versus parthenocarpic ovaries. Interestingly, fertilized ovaries recovered after FFI removal but parthenocarpic ones did not. In previous studies, we compared gene expression profiles of pollinated ovaries (committed to set fruit) with respect to those affected by FFI, and to non-pollinated ovaries (undergoing senescence). We selected cell wall invertases and trehalose-6-phosphate phosphatases (TPP) that could be associated with fruit set and assimilate partitioning. We successfully mutated two invertases and TPP family members in cucumber by CRISPR-Cas9 technology using two different vectors. We found that the Golden Braid system efficiently mutated simultaneously two DNA targets at both alleles.