Department of Biological Sciences, National Sun Yat-sen University, 804 Kaohsiung, Taiwan.
J Plant Physiol. 2012 Mar 15;169(5):529-41. doi: 10.1016/j.jplph.2011.12.004. Epub 2012 Jan 5.
In this report a full-length cDNA, SPCAM, was isolated from ethephon-treated mature leaves of sweet potato. SPCAM contained 450 nucleotides (149 amino acids) in its open reading frame, and exhibited high amino acid sequence identities (ca. 76-100%) with several plant calmodulins, including Arabidopsis, carrot, ghost needle weed, pea, potato, soybean, sweet chestnut, and tobacco. Sweet potato SPCAM also contained four putative conserved calmodulin EF-hand motifs, which responded for Ca(2+) binding and cellular signalling. Phylogenetic tree analysis showed that sweet potato SPCAM exhibited closely-related association with Arabidopsis AtCAM7, which functioned as a transcriptional regulator. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that SPCAM gene expression was not significantly increased from L1 immature leaf to L3 mature leaf, however, was remarkably enhanced in L4 early senescent leaf, and then decreased in L5 late senescent leaf. In dark- and ethephon-treated mature leaves, SPCAM expression was significantly increased from 6 to 48h, then decreased gradually until 72h after treatment. Ethephon-mediated leaf senescence, H(2)O(2) elevation, and senescence-associated gene expression, however, was remarkably inhibited by chlorpromazine, a calmodulin inhibitor. Exogenous application of purified calmodulin SPCAM fusion protein reversed the chlorpromazine repression of ethephon-mediated leaf senescence, H(2)O(2) elevation and senescence-associated gene expression. Based on these data we conclude that sweet potato SPCAM is an ethephon-inducible calmodulin and its expression is enhanced in natural and induced senescent leaves. Calmodulin SPCAM may play a physiological role in ethephon-mediated leaf senescence, H(2)O(2) elevation and senescence-associated gene expression in sweet potato leaves.
在本报告中，从乙烯利处理的甘薯成熟叶片中分离出全长 cDNA SPCAM。SPCAM 的开放阅读框包含 450 个核苷酸（149 个氨基酸），与几种植物钙调蛋白（包括拟南芥、胡萝卜、鬼针草、豌豆、马铃薯、大豆、甜栗和烟草）具有很高的氨基酸序列同一性（约 76-100%）。甘薯 SPCAM 还含有四个假定的保守钙调蛋白 EF 手基序，这些基序响应 Ca（2+）结合和细胞信号转导。系统发育树分析表明，甘薯 SPCAM 与拟南芥 AtCAM7 密切相关，后者作为转录调节剂发挥作用。逆转录-聚合酶链反应（RT-PCR）分析表明，SPCAM 基因表达从 L1 未成熟叶片到 L3 成熟叶片没有显著增加，但在 L4 早期衰老叶片中显著增强，然后在 L5 晚期衰老叶片中减少。在黑暗和乙烯利处理的成熟叶片中，SPCAM 表达从 6 小时到 48 小时显著增加，然后逐渐减少，直到处理后 72 小时。然而，氯丙嗪作为钙调蛋白抑制剂显著抑制了乙烯利介导的叶片衰老、H（2）O（2）升高和衰老相关基因的表达。外源性应用纯化的钙调蛋白 SPCAM 融合蛋白逆转了氯丙嗪对乙烯利介导的叶片衰老、H（2）O（2）升高和衰老相关基因表达的抑制作用。基于这些数据，我们得出结论，甘薯 SPCAM 是一种乙烯利诱导的钙调蛋白，其在自然和诱导衰老叶片中的表达增强。钙调蛋白 SPCAM 可能在乙烯利介导的甘薯叶片衰老、H（2）O（2）升高和衰老相关基因表达中发挥生理作用。
