Cloning And Expression Analysis Of Gene Encoding Receptor-Like Protein Kinase Gene From In Cut Gerbera Jamesonii

Gerbera(Gerbera jamesonii Bolus) has become the fifth largest cut flower in the world. However, A series of aging symptoms, including head drooping, stem bending and petal wilting, result in a short vase life in post-harvest Gerbera flower. Receptor-like protein kinase(RLK) is a key component in many signal transduction pathway in plants. In the present study, cut gerbera(Gerbera jamesonii Bolus‘Crossfire’) flowers were used as the experimental material, a gene, Gj RLK1 encoding RLK was cloned and characterized from gerbera petals. The organ specific expressions of Gj RLK1 gene and the expression pattern of Gj RLK1 in response to vasing of cut gerbera were investigated by real-time quantitative RT-PCR. The effects of low temperature, cytokinin or dark on the expression of Gj RLK1 gene in cut grbera were further investigated, and the regulation of the treatments on vase life was also determined. The main results were as follows:1. Through RT-PCR and RACE performance, a receptor-like kinase(RLK) gene, named as Gj RLK1, was cloned and characterized. The full length of Gj RLK1 c DNA consists of 2486 bp, including a 2157-bp open read frame encoding a polypeptide of 719 amino acids. The BLASTp analysis showed that Gj RLK1 is a member of typical leucine rich repeat receptor-like kinase(LRR-RLKs) family, cantaining an extracellular domain of the receptor with a ten-LRR-repeat motif, a transmembrane domain and an intracellular serine / threonine kinase domain. Multiple sequence alignment revealed that Gj RLK1 protein shares 73%, 71%, 67% and 63% sequence identity with cocao Tc RLK, Corchorus Cc RLK, Arabidopsis At RLK(At1g09970) and Medicago Mt RLK, respectively.2. The organ specific expressions of Gj RLK1 gene and the effect of low temperature on Gj RLK1 expression were investigated by using q RT-PCR, the results showed that Gj RLK1 gene was ubiquitiouly expressed in gerbera flowers, leaves and roots with higher expressions in ray florets and calyx. The expression of Gj RLK1 gene in cut gerbera was lightly downregulated first, and then rapidly upregulated in response to vasing, with a peak expression at the 18 th d of vasing, up to 3.03 times of the control. Low temperature of 4℃ for 24 h increased the expression of Gj RLK1 gene, and decreased the vase life of cut gerbera.3. The effects of dark treatment and cytokinin(6-BA) on the expression of Gj RLK1 gene and the vase life of cut gerbera were investigated, the results showed that dark treatment significantly upregulated the expression of Gj RLK1 gene, and promoted the senescence of cut gerbera by the evaluation of the vase life. The expression of Gj RLK1 gene was markedly downregulated by 6-BA, and the vase life of cut gerbera was increased. These observations show that cytokinin might retard the senescence of cut gerbera throuth downregulation of Gj RLK1 gene expression, and that dark may promote the senescence through upregulation of Gj RLK1 gene expression.