Drought stress responses revealed by genomic and transcriptomic analyses of two macrofungi (Inonotus hispidus and Inocutis levis) from Populus euphratica.

Abstract

Populus euphratica is a key deciduous and tall arbour capable of forming forests in arid and desert environments, exhibiting notable tolerance to drought, salinity and bacterial resistance. This study completed whole-genome sequencing of Inonotus hispidus and Inocutis levis, collected from Xinjiang, China, to predict genome structure and identify potential drought-related genes. Combined with transcriptome sequencing under different drought conditions simulated using PEG-6000, the gene expression regulation during drought tolerance was analysed. Whole-genome sequencing was carried out on the Illumina Novaseq and Pacbio Sequel platforms, resulting in genome size of 34.57 Mb for Inonotus hispidus and 37.17 Mb for Inocutis levis, respectively. A total of 10,169 and 10,140 protein-coding genes were annotated in these two species. The genomes of two species exhibited high synteny with 7,226 shared homologous genes and their functional annotations showed high similarity. Under drought stress at three PEG-6000 concentrations (10%, 30% and 50%), the transcriptomic analyses revealed 4,550 and 2,113 differentially expressed genes (DEGs) in the two fungi, respectively, with an increasing number of up- and down-regulated genes as the drought stress intensified. Gene expression profiles in response to drought stress showed prominent changes, amongst which the genes related to antioxidation, osmotic regulation, signal transduction and ribosomal function may play important roles. In the ribosome pathway, Inonotus hispidus showed a significant down-regulation of ribosomal-related genes under mild drought stress, which is up-regulated once again as the stress intensifies, while Inocutis levis exhibited significant up-regulation of these genes under severe drought stress, highlighting distinct drought adaptation strategies. This study provides essential theoretical insights into the molecular adaptation mechanisms of fungi in dry environments and offers new perspectives for the development of microbial resources in arid regions.