Trehalose-6-phosphate And SNF1-related Protein Kinase1Are Involved In The First-fruit Inhibition Of Cucumber(Cucumis Sativus L.)

In cucumber (Cucumis sativus L.), the preexisting fruits inhibit the growth of subsequent fruits. To study the mechanism underlying the predominant growth of the preexisting fruits, we examined the growth rate of fruit, sink activity, level of free sugars and the activities of SNF1-related protein kinase1(SnRK1) in the peduncle of two types of fruits. We found1、In two-fruit cucumber plants, the growth rate and sink activity (evaluated by alkaline alpha-galactosidase (CsAGA) activity in the peduncle) of the first fruit are higher than those of the second fruit.2、The14C labeling experiment revealed that assimilates produced by the leaves which are more close to the second fruit tend to move to the first fruit.3、The levels of sucrose and trehalose-6-phosphate (T6P) in the peduncle of the first fruit are higher than those of the second fruit. The SNF1-related protein kinase1(SnRK1) activity is lower in the peduncle of the first fruit than that of the second fruit from0to8days after anthesis.4、The growth rate and sink activity of the second fruit were enhanced by removing the first fruit or by treating the second fruit with6-benzyl aminopurine, comparing with an increase of sucrose and T6P levels and a decrease of SnRK1activity in the second fruit peduncle.5、The SnRKl activity was inhibited by T6P in an in vitro kniase assay, and the mRNA level of CsAGA1in cucumber calli was up-regulated by exogenous trehalose treatment, confirming that SnRK1activity and CsAGA1expression can be regulated by T6P. Our results suggest that the T6P and SnRK1mediated signaling are involved in the regulation of cucumber first-fruit inhibition.