Plant Gene Expression Laboratory, CSIR-National Botanical Research Institute (Council of Scientific and Industrial Research), Lucknow-226001, India.
J Exp Bot. 2011 Oct;62(14):5091-103. doi: 10.1093/jxb/err209. Epub 2011 Jul 15.
Abscission is a process that involves shedding of plant organs from the main plant body. In this study it is shown that the process of petal separation in the fragrant rose, Rosa bourboniana, is accompanied by the expression of two xyloglucan endotransglucosylase/hydrolase genes, RbXTH1 and RbXTH2. The sequences of the two genes show 52% amino acid identity but are conserved at the catalytic site. The genes are up-regulated soon after the initiation of the abscission process and their transcription is associated with the progression of abscission, being faster in ethylene-treated flowers but slower during field abscission. Transcription is ethylene responsive, with the ethylene response being tissue-specific for RbXTH1 but largely tissue-independent for RbXTH2. Expression is correlated with an increase in xyloglucan endotransglucosylase (XET) action in petal abscission zones of both ethylene-treated and field abscising flowers. Proximal promoters of both the genes drive β-glucuronidase expression in an ethylene-responsive and abscission-related manner in agrobacteria-infiltrated rose petals, indicating that cis-elements governing ethylene-responsive and abscission-related expression probably lie within the first 700 nucleotides upstream of the translational initiation codon. The results show that cell wall remodelling of the xyloglucan moieties through the XET action of XTHs may be important for cell separation during abscission.
离区是一个将植物器官从母体上脱落的过程。本研究表明，在芳香的香水月季（Rosa bourboniana）中花瓣分离的过程伴随着两个木葡聚糖内转糖基酶/水解酶基因（RbXTH1 和 RbXTH2）的表达。这两个基因的序列显示出 52%的氨基酸同一性，但在催化位点保守。这两个基因在离区开始后很快上调，其转录与离区的进展有关，在乙烯处理的花朵中更快，但在田间离区时较慢。转录对乙烯有反应，RbXTH1 的乙烯反应具有组织特异性，但 RbXTH2 的乙烯反应在很大程度上是组织非依赖性的。表达与木葡聚糖内转糖基酶（XET）在乙烯处理和田间离区花朵的花瓣离区带中的作用增加相关。这两个基因的近端启动子以乙烯反应和与离区相关的方式驱动β-葡萄糖醛酸酶在农杆菌浸润的玫瑰花瓣中的表达，表明调控乙烯反应和与离区相关的表达的顺式元件可能位于翻译起始密码子上游的前 700 个核苷酸内。结果表明，通过 XTHs 的 XET 作用对木葡聚糖部分的细胞壁重塑可能对离区过程中的细胞分离很重要。
