Nishikawa Fumie, Kato Masaya, Hyodo Hiroshi, Ikoma Yoshinori, Sugiura Minoru, Yano Masamichi
The United Graduate School of Agricultural Science, Gifu University, Shizuoka University, Yanagido, Gifu, 501-1193 Japan.
J Exp Bot. 2003 Nov;54(392):2439-48. doi: 10.1093/jxb/erg283. Epub 2003 Sep 25.
The ascorbate content declined rapidly in broccoli (Brassica oleracea L. var. italica) florets, but not in the stem tissue, during post-harvest senescence. Ascorbate peroxidase (APX), ascorbate oxidase (AO), l-galactono-1,4-lactone dehydrogenase (GLDH), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were investigated in gene expression after harvest in both florets and the stem tissue of broccoli. Cytosolic gene expressions (BO-APX 1, BO-APX 2, BO-AO, BO-MDAR 2, and BO-GR) were stimulated actively in broccoli florets after harvest. By contrast, it was observed that mRNA levels of chloroplastic APX, BO-sAPX and BO-tbAPX, had decreased by 12 h after harvest in broccoli florets, suggesting that the active oxygen species (AOS) scavenging system in chloroplasts was largely abolished in florets during the early hours of the post-harvest period. In addition, gene expressions in GLDH and other chloroplastic enzymes such as BO-MDAR 1 and BO-DHAR decreased rapidly within 24 h after harvest. Ethylene treatment had no effect on the ascorbate level and the expression of all genes investigated. The expressions of BO-GLDH and chloroplastic genes (BO-sAPX, BO-tbAPX, BO-MDAR 1, and BO-DHAR) mRNA were suppressed by treatment with methyl jasmonate (MJ) and abscisic acid (ABA) and were accompanied by the acceleration of ascorbate degradation. These data suggest that ascorbate metabolism tends to be inactivated in chloroplasts by transcriptional regulation, but not in the cytosol, when ascorbate decreases under stress conditions.
在采后衰老过程中，西兰花（Brassica oleracea L. var. italica）小花中的抗坏血酸含量迅速下降，但茎组织中抗坏血酸含量未下降。对西兰花小花和茎组织采后基因表达情况进行了研究，分析了抗坏血酸过氧化物酶（APX）、抗坏血酸氧化酶（AO）、L-半乳糖-1,4-内酯脱氢酶（GLDH）、单脱氢抗坏血酸还原酶（MDAR）、脱氢抗坏血酸还原酶（DHAR）和谷胱甘肽还原酶（GR）。采后西兰花小花中胞质基因表达（BO-APX 1、BO-APX 2、BO-AO、BO-MDAR 2和BO-GR）被积极激活。相比之下，观察到采后12小时西兰花小花中叶绿体APX（BO-sAPX和BO-tbAPX）的mRNA水平下降，这表明采后早期小花叶绿体中的活性氧清除系统在很大程度上被破坏。此外，采后24小时内GLDH以及其他叶绿体酶（如BO-MDAR 1和BO-DHAR）的基因表达迅速下降。乙烯处理对抗坏血酸水平和所有研究基因的表达均无影响。用茉莉酸甲酯（MJ）和脱落酸（ABA）处理可抑制BO-GLDH和叶绿体基因（BO-sAPX、BO-tbAPX、BO-MDAR 1和BO-DHAR）mRNA的表达，并伴随着抗坏血酸降解加速。这些数据表明，在胁迫条件下抗坏血酸含量下降时，叶绿体中的抗坏血酸代谢倾向于通过转录调控失活，但胞质中并非如此。
