ROLE OF EXPANSIN AND XTH DURING ROSE FLOWER OPENING

Abstract

Flower opening involving petal growth from bud to full bloom should be enjoyed by consumers. If the speed of petal growth could be controlled and petals made to open fully, cut roses might be enjoyed for longer. Petal growth is mainly due to the expansion of petal cells. However, it has been proposed that when the cell wall remains rigid, cell expansion does not occur. Expansin and xyloglucan endotransglycosylase/hydrolase (XTH) are known as representative proteins that loosen cell wall in plant. In our study, we are trying to clarify how these proteins involve in petal growth of rose and contribute to improvement of rose vase life. First, petal cell wall extensibility was analyzed. Proteins extracted from cell wall fraction of the petals were suggested to have a positive effect on petal cell wall extensibility. We have isolated three expansin cDNAs and four XTH cDNAs from rose petal and analyzed their mRNA expression using primers that recognize all of their paralogs during petal growth. The results showed that mRNA transcripts level exclusively correlated to petal growth. Further, to clarify the functions of expansin and XTH in more detail, we are now analyzing the phenotype of the petal using a model plant, eustoma, which expansin and XTH were knocked down by RNAi technique.