Vacuole Cysteine Proteases and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Degradation during Monocarpic Senescence in Cowpea Leaves

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• 作者：B. Srivalli ; Sudhakar Bharti and Renu Khanna-Chopra
• 关键词：endopeptidase ; iodoacetamide ; net photosynthetic rate ; D ; L ; norleucine ; phenyl methyl sulphonyl fluoride ; pod ; proteins ; Vigna unguiculata
• 刊名：Photosynthetica
• 出版年：2001
• 出版时间：2001
• 年：2001
• 卷：39
• 期：1
• 页码：87-93
• 全文大小：880 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Plant Physiology
  
• 出版者：Springer Netherlands
• ISSN：1573-9058

文摘

Characterisation of proteases degrading ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO, EC: 4.1.1.39) was studied in the cowpea leaf during monocarpic senescence 3 and 9 d after flowering (DAF), representing early and mid pod fill. The stage at 3 DAF coincided with decrease in the metabolic parameters characterising senescence, i.e., contents of total soluble proteins, RuBPCO, and leaf nitrogen. At 9 DAF, there was a decline in total soluble proteins and an appearance of a 48 kDa cysteine protease. Characterisation of the proteases was done using specific inhibitors. Subcellular localisation at 3 DAF was studied by following the degradation of RuBPCO large subunit (LSU) in the vacuole lysates using immunoblot analyses. Cysteine proteases played a predominant role in the degradation of RuBPCO LSU at the crude extract level. At 9 DAF, expression of cysteine protease isoforms was monitored using polyclonal antibodies against papain and two polypeptides of molecular masses 48 and 35 kDa were observed in the vacuole lysates. We confirmed thus the predominance of cysteine proteases in the vacuoles during different stages of pod development in cowpea leaf.