Ye Z H, Droste D L
Department of Biology, Washington University, St. Louis, MO 63130, USA.
Plant Mol Biol. 1996 Feb;30(4):697-709. doi: 10.1007/BF00019005.
The study of plant ribonuclease (RNase) functions is complicated by a complex profile of RNase activities detected in tissues. Thus, isolation of individual RNase genes will be desirable for the further understanding of function of each RNase. Here, we describe the isolation of cDNAs encoding two RNases, ZRNaseI and ZRNaseII, in differentiating tracheary elements (TEs) induced from isolated mesophyll cells of Zinnia elegans. Both the ZRNaseI and ZRNaseII exhibit putative secretion signal sequences at the amino-terminal ends with predicted molecular masses of 24 247 Da and 22 448 Da as mature proteins, respectively. DNA gel blot analysis showed that both RNases in Zinnia appear to be encoded by a small gene family. RNA gel blot analysis showed that the expression of the ZRNaseI gene was associated with the late stage of in vitro TE differentiation, whereas the ZRNaseII gene was mainly induced in response to stress. Neither RNase gene was induced in response to phosphate starvation, or to H2O2 challenge in the cultured mesophyll cells, or to senescence in the leaves. In young leaves, the ZRNaseI gene was not induced in response to wounding. But the ZRNaseII gene was markedly induced by 6 h after wounding. Tissue print hybridization showed that the expression of the ZRNaseI gene was preferentially associated with the differentiation TEs in Zinnia stems, while the ZRNaseII mRNA was not detected in unwounded Zinnia organs. Taken together, the results indicated that the ZRNaseI gene is expressed during the process of xylogenesis both in vitro and in the plant, whereas the ZRNaseII gene is predominantly induced in response to wounding. The identification of these RNase genes provides molecular tools for the dissection of the process of autolysis during xylogenesis, and for the dissection of the role of RNase in wounding response.
植物核糖核酸酶（RNase）功能的研究因在组织中检测到的复杂RNase活性谱而变得复杂。因此，分离单个RNase基因对于进一步了解每种RNase的功能是必要的。在此，我们描述了从百日草分离的叶肉细胞诱导分化的管状分子（TEs）中，编码两种RNase，即ZRNaseI和ZRNaseII的cDNA的分离。ZRNaseI和ZRNaseII在氨基末端均显示出假定的分泌信号序列，作为成熟蛋白，预测分子量分别为24247 Da和22448 Da。DNA凝胶印迹分析表明，百日草中的两种RNase似乎都由一个小基因家族编码。RNA凝胶印迹分析表明，ZRNaseI基因的表达与体外TE分化的后期相关，而ZRNaseII基因主要是在应激反应中被诱导。在培养的叶肉细胞中，两种RNase基因均未因磷酸盐饥饿、H2O2刺激或叶片衰老而被诱导。在幼叶中，ZRNaseI基因不会因伤口而被诱导。但ZRNaseII基因在受伤后6小时会被显著诱导。组织印迹杂交表明，ZRNaseI基因的表达优先与百日草茎中的分化TEs相关，而在未受伤的百日草器官中未检测到ZRNaseII mRNA。综上所述，结果表明ZRNaseI基因在体外和植物体内的木质化过程中均有表达，而ZRNaseII基因主要是在伤口反应中被诱导。这些RNase基因的鉴定为剖析木质化过程中的自溶过程以及RNase在伤口反应中的作用提供了分子工具。
