构巢曲霉硫代谢关键转录调控因子MetR严格调控光敏色素依赖型红光响应过程

The sulfur metabolism regulator MetR is a global regulator controlling phytochrome-dependent light responses in Aspergillus nidulans

真菌可以利用光敏色素(phytochrome)感受红光,在构巢曲霉中,光敏色素Fph A感受红光后激活下游压力响应Hog A/Sak A信号通路,控制相关基因的表达,最终抑制菌体有性生殖过程,促进菌体无性分生孢子的产生.构巢曲霉中转录调控因子Met R是调控硫代谢的关键因子.本研究发现,met R基因突变株不能表达光敏色素编码基因fph A.同时,与次级代谢产物合成相关的多个基因簇在met R基因突变株中出现显著的上调或下调.进一步研究发现,转录调控因子Met R通过严格调控光敏色素Fph A编码基因的表达控制Hog A/Sak A信号通路,进而调控菌体红光响应过程.本研究证明,构巢曲霉中硫代谢关键调控因子Met R是一个全局性调控因子,除调控硫代谢外,还可以严格调控菌体光响应和次级代谢等过程.

Phytochrome-dependent light signaling has been studied in several fungi.In Aspergillus nidulans lightstimulated phytochrome activates the high-osmolarity glycerol(HOG)signaling pathway and thereby controls the expression of a large number of genes,many of which are related to stress responses.In a genome-wide expression analysis in A.nidulans we found that phytochrome,fph A,is under strict expression control of the central regulator of the sulfur-starvation response,Met R.This transcriptional regulator is required for the expression of genes involved in inorganic sulfur assimilation.In the presence of organic sulfur,Met R is probably ubiquitinated and possibly degraded and the transcription of sulfur-assimilation genes,e.g.,sulfate permease,is turned off.The expression analysis described here revealed,however,that Met R additionally controls the expression of hundreds of genes,many of which are required for secondary metabolite production.We also show that met R mutation phenocopies fph A deletion,and five other histidine-hybrid kinases are down-regulated in the met R1 mutant.Furthermore,we found that light and phytochrome regulate the expression of at least three carbon–sulfur hydrolases.This work is a further step towards understanding the interplay between light sensing and metabolic pathways.