Gomes-Filho Enéas, Lima Carmen Rogélia Farias Machado, Costa José Hélio, da Silva Ana Cláudia Marinho, da Guia Silva Lima Maria, de Lacerda Claudivan Feitosa, Prisco José Tarquinio
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, P.O. Box 6039, 60455-900, Fortaleza, Ceará, Brazil.
Plant Cell Rep. 2008 Jan;27(1):147-57. doi: 10.1007/s00299-007-0433-5. Epub 2007 Sep 27.
Pitiúba cowpea [Vigna unguiculata (L.) Walp] seeds were germinated in distilled water (control treatment) or in 100 mM NaCl solution (salt treatment), and RNase was purified from different parts of the seedlings. Seedling growth was reduced by the NaCl treatment. RNase activity was low in cotyledons of quiescent seeds, but the enzyme was activated during germination and seedling establishment. Salinity reduced cotyledon RNase activity, and this effect appeared to be due to a delay in its activation. The RNases from roots, stems, and leaves were immunologically identical to that found in cotyledons. Partially purified RNase fractions from the different parts of the seedling showed some activity with DNA as substrate. However, this DNA hydrolyzing activity was much lower than that of RNA hydrolyzing activity. The DNA hydrolyzing activity was strongly inhibited by Cu(2+), Hg(2+), and Zn(2+) ions, stimulated by MgCl(2), and slowly inhibited by EDTA. This activity from the most purified fraction was inhibited by increasing concentrations of RNA in the reaction medium. It is suggested that the major biological role of this cotyledon RNase would be to hydrolyze seed storage RNA during germination and seedling establishment, and it was discussed that it might have a protective role against abiotic stress during later part of seedling establishment.
皮蒂乌巴豇豆[Vigna unguiculata (L.) Walp]种子在蒸馏水（对照处理）或100 mM NaCl溶液（盐处理）中萌发，然后从幼苗的不同部位纯化核糖核酸酶。NaCl处理降低了幼苗的生长。静止种子子叶中的核糖核酸酶活性较低，但该酶在萌发和幼苗形成过程中被激活。盐度降低了子叶核糖核酸酶活性，这种影响似乎是由于其激活延迟所致。根、茎和叶中的核糖核酸酶在免疫上与子叶中的核糖核酸酶相同。从幼苗不同部位部分纯化的核糖核酸酶组分以DNA为底物时表现出一定活性。然而，这种DNA水解活性远低于RNA水解活性。DNA水解活性受到Cu(2+)、Hg(2+)和Zn(2+)离子的强烈抑制，受到MgCl(2)的刺激，并受到EDTA的缓慢抑制。反应介质中RNA浓度增加会抑制最纯组分的这种活性。研究表明，这种子叶核糖核酸酶的主要生物学作用可能是在萌发和幼苗形成过程中水解种子储存的RNA，并且讨论了它可能在幼苗形成后期对非生物胁迫具有保护作用。
