title: Cowpea ribonuclease: properties and effect of NaCl-salinity on its activation during seed germination and seedling establishment.
abstract: 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.
authors: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, P.O. Box 6039, 60455-900, Fortaleza, Ceará, Brazil. egomesf@ufc.br
authors: Enéas
authors: E
authors: Gomes-Filho
authors: Carmen Rogélia Farias Machado
authors: CR
authors: Lima
authors: José Hélio
authors: JH
authors: Costa
authors: Ana Cláudia Marinho
authors: AC
authors: da Silva
authors: Maria
authors: M
authors: da Guia Silva Lima
authors: Claudivan Feitosa
authors: CF
authors: de Lacerda
authors: José Tarquinio
authors: JT
authors: Prisco
mesh_terms: D018548:Cotyledon / Q000187:drug effects / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D007887:Fabaceae / Q000187:drug effects / Q000201:enzymology*; D018525:Germination / Q000187:drug effects; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism*; D012260:Ribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D054712:Salinity; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology*; D012639:Seeds / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D010940:Plant Proteins; D012965:Sodium Chloride; D012260:Ribonucleases