Abstract
The developing fruit undergoes phase of cell division and expansion followed by numerous metabolic changes leading to ripening. In Japanese pear, exogenous GAs have been widely used to increase fruit enlargement. Exogenous application of GA 3+4 paste until 40 days after anthesis to the young fruit results in increased fruit size. However, the molecular mechanism of fruit development has not understood yet. Here, we have searched genes related to GA-induced fruit enlargement in pear by microarray analysis. Pear fruit was treated with GA1, GA3, GA4, GA4+Prohexadione calcium (GA4P) in lanolin paste at five weeks after full bloom (WAF) and the fruit were sampled at two week after the treatment (at 7 WAF). Total RNA was extracted from the above samples. Among these treatments, GA4 and GA4+Prohexadione calcium resulted in getting larger fruit. A custom oligoarray of Japanese pear based on 9,812 independent ESTs was used for comprehensive investigation of gene expression after GA4 and (GA4P) treatments. Up-regulated 4 genes and down-regulated 7 genes were identified. Expression of up- and down-regulated genes was examined by quantitative RT-PCR during fruit development. Expression of up-regulated 3 genes showed remarkable increase after full bloom and that of down-regulated 4 genes showed decrease trend during fruit development. Total 7 (3 up-regulated and 4 down regulated) genes were selected for further transgenic experiment to clarify the role of fruit cell elongation.
