Köck M, Stenzel I, Zimmer A
Martin Luther University Halle-Wittenberg, Biocenter, D-06120 Halle, Germany.
J Exp Bot. 2006;57(14):3717-26. doi: 10.1093/jxb/erl124. Epub 2006 Sep 21.
Ribonuclease LX (RNaseLX) from tomato (Solanum lycopersicum L.) belongs to the RNase T2/S-RNase superfamily of plant endoribonucleases and this is a report on the characterization of the RNaseLX gene and its encoded protein as a member of the phosphate starvation response in tomato. RNaseLX gene sequences were cloned by a PCR-assisted approach. RNaseLX promoter sequences contained the conserved binding motif of the transcription factor PHR1 known to mediate phosphate starvation-dependent gene expression. The increase of RNaseLX transcript levels in roots during phosphate starvation correlated with high promoter activity in transgenic plants carrying a PromLX::uidA gene construct and pointed to transcriptional control of RNaseLX expression. Histochemical staining for beta-glucuronidase activity and immunodetection of RNaseLX protein revealed striking RNaseLX expression in main and lateral root tips of phosphate-starved transgenic plants, specifically in epidermal cells, as well as in lateral and adventitious root primordia. Induced RNaseLX expression in roots correlated with stimulated growth and elongation of primary and lateral roots during phosphate deprivation. Phosphate-starvation-induced RNaseLX transcript levels in roots were not modulated by auxin or ethylene. These data indicate that the role of intracellular RNaseLX in the phosphate starvation response is connected with specific RNA turnover processes at the root tip.
来自番茄（Solanum lycopersicum L.）的核糖核酸酶LX（RNaseLX）属于植物内切核糖核酸酶的RNase T2/S-RNase超家族，本文报道了RNaseLX基因及其编码蛋白作为番茄磷饥饿反应成员的特性。通过PCR辅助方法克隆了RNaseLX基因序列。RNaseLX启动子序列包含已知介导磷饥饿依赖性基因表达的转录因子PHR1的保守结合基序。在磷饥饿期间，根中RNaseLX转录水平的增加与携带PromLX::uidA基因构建体的转基因植物中的高启动子活性相关，表明RNaseLX表达受转录调控。β-葡萄糖醛酸酶活性的组织化学染色和RNaseLX蛋白的免疫检测显示，在磷饥饿的转基因植物的主根和侧根根尖中，特别是在表皮细胞以及侧根和不定根原基中，RNaseLX有显著表达。根中诱导的RNaseLX表达与磷缺乏期间主根和侧根的生长和伸长受刺激相关。根中磷饥饿诱导的RNaseLX转录水平不受生长素或乙烯的调节。这些数据表明，细胞内RNaseLX在磷饥饿反应中的作用与根尖特定的RNA周转过程有关。
