瑞氏木霉木糖代谢关键酶基因在不同碳源条件下的表达

EXPRESSION OF XYLOSE METABOLIC KEY GENES OF TRICHODERMA REESEI ON VARIOUS CARBON SOURCES MEASURED BY A SERIES OF NORTHERN HYBRIDIZATIONS

用２０ 种不同的碳源（ 包括单一碳源和混合碳源） 分别培养瑞氏木霉（ Ｔｒｉｃｈｏｄｅｒｍａｒｅｅｓｅｉ）ＱＭ９４１４ 。通过一系列Ｎｏｒｔｈｅｒｎ 杂交分析检测瑞氏木霉木糖还原酶（ＸＲ） ，木糖醇脱氢酶（ＸＤＨ） 以及转醛醇酶（ＴＡＬ） ｍ ＲＮＡ 的表达情况。实验结果证实，槐糖和木二糖是ｘｒ 和ｘｄｈ 表达的强诱导物，阿拉伯糖和乳糖也有较强的诱导作用。葡萄糖在培养基中的存在阻遏该二基因的表达。当葡萄糖耗尽以后，培养基中不存在任何诱导物的情况下，ｘｒ 和ｘｄｈ 以一定的基础水平进行转录。相比较，ｔａｌ

The expression of xylose reductase (XR), xylitol dehydrogenase (XDH) and transaldolase (TAL) genes from Trichoderma reesei , measured by Northern hybridization, were studied by adding different carbon sources (20 kinds, including single and mixed carbon sources) separately into the basal medium on which T.reesei QM9414 was grown. The experiment results indicated that the two disaccharides: sophrose and xylibiose act as a strong inducer for the expression of xr and xdh. The lactose and arabinose were identified as inducer also. The presence of glucose repressed the transcription of xr and xdh. When glucose depleted. xr and xdh were expressed at certain level, implying that expression of xr and xdh are controlled by the carbon catabolite repression mechanism and there existed a constitutive base level's expression of xr and xdh when the catabolite repression mechanism was derepressed. On the other hand, transaldolase gene strongly expressed on all the carbon sources used.