近日,，國際學(xué)術(shù)刊物Eukaryotic Cell發(fā)表了中科院天津工業(yè)生物技術(shù)研究所田朝光課題組關(guān)于半纖維素降解調(diào)控機制的研究論文。田朝光課題組與加州大學(xué)合作,，解析了粗糙脈孢菌半纖維素降解基因xlr-1調(diào)控靶體,，揭示了粗糙脈孢菌與其它絲狀真菌在半纖維素降解和調(diào)控機制上的相似性和不同點。
半纖維素是僅次于纖維素的第二大豐富的可再生生物質(zhì)資源,。絲狀真菌對半纖維素的降解作用需要很多不同的酶,，這些酶是由生物質(zhì)降解后的分子或者其衍生物誘導(dǎo)產(chǎn)生的,，并且主要在轉(zhuǎn)錄水平進(jìn)行調(diào)控,。但是人們對具體的調(diào)控機理還不是很清楚，為了更好地利用半纖維素,，研究這一機理也就成為必然,。
研究人員在粗糙脈孢菌體系為研究對象，以木聚糖為唯一碳源,，通過轉(zhuǎn)錄組學(xué)分析鑒定了353個基因被半纖維素顯著誘導(dǎo),。在預(yù)測的19個半纖維素酶基因中，8個基因顯著誘導(dǎo)表達(dá),。
通過進(jìn)一步的分泌蛋白質(zhì)組學(xué)和基因敲除突變體庫的篩選,，研究人員發(fā)現(xiàn)，在曲霉和木霉上的轉(zhuǎn)錄因子XlnR/Xyr1的同源基因NCU06971是粗糙脈孢菌半纖維素主調(diào)控因子,，并命名為xlr-1（木聚糖酶調(diào)節(jié)因子1）,。xlr-1缺失突變株在木聚糖和木糖上都不能生長，但是可以在纖維素上生長并且只對纖維素水解能力有輕微影響,。
為了研究半纖維素降解的調(diào)節(jié)機制,，該研究組在木糖、木聚糖分解和纖維素分解條件下探明了XLR-1蛋白的調(diào)控靶體,，XLR-1蛋白在粗糙脈孢菌中調(diào)節(jié)主要的半纖維素酶基因,，但對部分纖維素酶的完全誘導(dǎo)有影響。此項研究對半纖維素降解調(diào)節(jié)機制的研究具有重要參考意義。（生物谷Bioon.com）
doi:10.1128/EC.05327-11
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Deciphering transcriptional regulatory mechanisms associated with hemicellulose degradation in Neurospora crassa
Jianping Sun, Chaoguang Tian, Spencer Diamond and N. Louise Glass
Hemicellulose, the second most abundant plant biomass fraction after cellulose, is widely viewed as a potential substrate for the production of liquid fuels and other value-added materials. Degradation of hemicellulose by filamentous fungi requires production of many different enzymes, which are induced by biopolymers or its derivatives and regulated mainly at the transcriptional level through transcription factors (TFs). Neurospora crassa, a model filamentous fungus, expresses and secretes enzymes required for plant cell wall deconstruction. To better understand genes specifically associated with degradation of hemicellulose, we applied secretome and transcriptome analysis to N. crassa grown on beechwood xylan. We identified 34 secreted proteins and 353 genes with elevated transcription on xylan. The xylanolytic phenotype of strains with deletions in genes identified from the secretome and transcriptome analysis of wild type was assessed, revealing functions for known and unknown proteins associated with hemicellulose degradation. By evaluating phenotypes of strains containing deletions of predicted TF genes in N. crassa, we identified a TF (xylan degradation regulator-1) essential for hemicellulose degradation that is an ortholog to XlnR/Xyr1 in Aspergillus and Trichoderma species, respectively, a major transcriptional regulator of genes encoding both cellulases and hemicellulases. Deletion of xlr-1 in N. crassa abolished growth on xylan and xylose, but growth on cellulose and cellulolytic activity was only slightly affected. To determine regulatory mechanisms for hemicellulose degradation, we explored the transcriptional regulon of XLR-1 under xylose, xylanolytic and cellulolytic conditions. XLR-1 regulated only some predicted hemicellulase genes in N. crassa and was required for a full induction of several cellulase genes. Hemicellulase gene expression was induced by a combination of release from carbon catabolite repression (CCR) and induction. This systematic analysis illustrates the similarities and differences in regulation of hemicellulose degradation among filamentous fungi.
