Brummell D A, Bird C R, Schuch W, Bennett A B
Department of Vegetable Crops, University of California, Davis 95616, USA.
Plant Mol Biol. 1997 Jan;33(1):87-95. doi: 10.1023/a:1005733213856.
Plant developmental processes involving modifications to cell wall structure, such as cell expansion, organ abscission and fruit ripening, are accompanied by increased enzyme activity and mRNA abundance of endo-1,4-beta-glucanases (EGases). An EGase cDNA clone, Cel4, isolated from tomato (Lycopersicon esculentum) has been shown to be identical to a tomato pistil-predominant EGase cDNA, TPP18. In addition to its previously reported expression during certain stages of early pistil development, Cel4 mRNA was also detected at high levels in the growing zones of etiolated hypocotyls (about 2.5-fold less than in pistils) and in young expanding leaves (about 3.5-fold less than in pistils). The abundance of Cel4 mRNA declined precipitously in older tissues as cells became fully expanded, and was barely detectable in mature vegetative tissues. Cel4 mRNA abundance was also low in abscission zones, and did not increase as abscission progressed. In fruit, Cel4 mRNA was present at low levels during fruit expansion, but was essentially absent during subsequent fruit development and ripening. Treatment of etiolated hypocotyls with ethylene or high concentrations of auxin sufficient to induce rapid lateral cell expansion and hypocotyl swelling also brought about an approximate doubling of Cel4 mRNA abundance, suggesting that Cel4 mRNA accumulation may be promoted directly or indirectly by ethylene. Thus, accumulation of Cel4 mRNA was found to be correlated with rapid cell expansion in pistils, hypocotyls and leaves.
涉及细胞壁结构修饰的植物发育过程，如细胞扩张、器官脱落和果实成熟，都伴随着内切-1,4-β-葡聚糖酶（EGases）的酶活性增加和mRNA丰度增加。从番茄（Lycopersicon esculentum）中分离出的一个EGase cDNA克隆Cel4，已被证明与番茄雌蕊优势EGase cDNA TPP18相同。除了之前报道的在雌蕊早期发育的某些阶段表达外，在黄化胚轴的生长区（比雌蕊中低约2.5倍）和幼嫩的正在扩展的叶片中（比雌蕊中低约3.5倍）也检测到高水平的Cel4 mRNA。随着细胞完全扩张，Cel4 mRNA在较老组织中的丰度急剧下降，在成熟营养组织中几乎检测不到。Cel4 mRNA在脱落区的丰度也很低，并且随着脱落过程的进行没有增加。在果实中，Cel4 mRNA在果实膨大期间含量较低，但在随后的果实发育和成熟过程中基本不存在。用乙烯或足以诱导快速横向细胞扩张和胚轴肿胀的高浓度生长素处理黄化胚轴，也使Cel4 mRNA丰度大约增加了一倍，这表明Cel4 mRNA的积累可能直接或间接受乙烯促进。因此，发现Cel4 mRNA的积累与雌蕊、胚轴和叶片中的快速细胞扩张相关。
