Cloning， characterization and expression of xyloglucan endotransglucosylase/hydrolase and expansin genes associated with petal growth and development during carnation flower opening
Harada T, Torii Y, Morita S, Onodera R, Hara Y, Yokoyama R, Nishitani K, Satoh S
J. Exp. Bot. 62:815-823
Growth of petal cells is a basis for expansion and morphogenesis 47 (outward-bending) of petals during opening of carnation flowers (Dianthus 48 caryophyllus L.). Petal growth progressed through elongation in the early 49 stage, expansion with outward-bending in the middle stage and expansion 50 of whole area in the late stage of flower opening. In the present study, four 51 cDNAs encoding xyloglucan endotransglucosylase/hydrolase (XTH) 52 (DcXTH1-4) and three cDNAs encoding expansin (DcEXPA1-3) were 53 cloned from petals of opening carnation flowers and characterized. 54 Real-time RT-PCR analyses showed that transcript levels of XTH and 55 expansin genes accumulated differently in floral and vegetative tissues of 56 carnation plants with opening flowers, indicating regulated expression of 57 these genes. DcXTH2 and DcXTH3 transcripts were detected in a large 58 amount in petals as compared with other tissues. DcEXPA1 and DcEXPA2 59 transcripts were markedly accumulated in petals of opening flowers. The 60 action of XTH in growing petal tissues was confirmed by in situ staining of 61 xyloglucan endotransglucosylase (XET) activity using a 62 rhodamine-labelled xyloglucan nonasaccharide as a substrate. Based on the 63 present findings, we suggest that two XTH genes (DcXTH2 and 3) and two 64 expansin genes (DcEXPA1 and 2) are associated with petal growth and 65 development during carnation flower opening.