Identification of genes involved in nigeran synthesis under nitrogen-starved condition in Aspergillus luchuensis

Some Aspergillus and Penicillium species specifically produce nigeran in the cell wall, which is an unbranched D-glucan consisting of alternating a-1,3- and a-1,4-glucoside linkages, under the nitrogen-starved condition. In this study, to identify the nigeran synthase gene in Aspergillus luchuensis, a nigeran producing filamentous fungi, we performed RNA-seq analysis under the presence of nitrogen source or not. One of the putative a-1,3-glucan synthase genes whose transcriptional levels were upregulated under nitrogen-starved condition was demonstrated to encode nigeran synthase not a-1,3-glucan synthase. Furthermore, two genes encoding an a-glucanosyltransferase and a hypothetical protein were involved in nigeran synthesis in term of controlling the nigeran content and molecular weight.