Abstract:

Four xyloglucan endotransglucosylase/hydrolase genes that related to cell wall loosen were
cloned from chrysanthemum and named as CmXTH1，CmXTH2，CmXTH3 and CmXTH4. Sequences
analysis showed that the N-terminal regions of deduced amino acid sequences all had signal peptides
composed of 20–30 amino acids，conserved catalytic sites of DE（I/L）DEFLG and N-glycosylation sites composed of N（R/A）T，CmXTH1/2/3 had four cysteine in C-terminal regions，the identity of 4 CmXTH1/2/3/4
was 66.2%. The phylogenetic analysis result suggested that CmXTH1/2/3 belongs to groupⅠof XTH
family，CmXTH4 belongs to groupⅡ. The real-time PCR results showed that：（1）CmXTH1/2/3/4 all had
expression in root，stem and leaf. CmXTH1 was highly expressed in chrysanthemum root. CmXTH2/3 was
expressed more in stem. CmXTH4 was highly expressed in alabastrum.（2）CmXTH1/2/3/4 showed
different expression levels in different parts of inflorescence. CmXTH1/4 was expressed more in ray florets.
CmXTH2/3 was expressed more in tubular florets. （3）CmXTH1/2/3/4 showed different expression levels in
different stages of ray florets development. CmXTH1/2 was highly expressed in ray florets at bloom stage，
CmXTH3 was highly expressed at senescent stage，while CmXTH4 was expressed highest at initiation stage.
The virus induced gene silence results showed that，the inflorescences diameters and ray florets lengths of
CmXTH1/2/3/4-silenced groups all showed decrease compared with control，the CmXTH4-silenced group
decreased most by 25.67% and 10.42% respectively，the sizes of petal epidermal cells decreased
obviously，influenced the extension of ray floret petal. The stamen length of CmXTH2-silenced tubular
florets and the diameter of CmXTH4-silenced sepal all showed significant decrease compared with control.
These results indicated that CmXTH1/2/3/4 participated in the opening of inflorescences，promoted the
extension of ray floret petal ， and they were important for the enlargement of chrysanthemum
inflorescences.

Key words: Chrysanthemum morifolium, petal, CmXTH, gene expression, gene silence