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Rho GTPases regulate the activity of cell wall biosynthesis, actin assembly and polar cell secretion. However, the function of Rho GTPase in filamentous fungi is poorly understood. To understand the role of Rho2 GTPase in Fusarium oxysporum, which is one of root rot pathogens of Panax notoginseng, △rho2 mutant was constructed. Phenotypes of △rho2, including conidiation, germination of spores, stresses (osmotic-, cell membrane-, cell wall disturbing-, metal-, and high temperature-) tolerance and pathogenicity were analyzed. The results showed that the growth of △rho2 was destroyed under cell wall disturbing stress and high temperature stress, suggesting that Rho2 regulated the response of F. oxysporum to cell wall synthesis inhibitors and high temperature stress. Germination of spores and pathogenicity to P. notoginseng were reduced in △rho2 mutant. Western blot results showed that rho2 deletion increased the phosphorylation level of Mpk1. To identify genes regulated by Rho2, transcriptome sequencing was carried out. 2477 genes were identified as upregulated genes and 2177 genes were identified as downregulated genes after rho2 was deleted. These genes provide clues for further study of rho2 function., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Lipids synthesized by oleaginous yeasts are considered to be the best candidates for biodiesel production. Cryptococcus humicola as an oleaginous yeast accumulated lipid in cells. In order to optimize the conditions for lipid production, different carbon and nitrogen sources were used and metals were added into the medium. Ca 2+ addition increased the lipid production greatly. Xylose and peptone were optimal carbon source and nitrogen source, respectively for lipid accumulation. Response surface experiment results revealed that the accumulation of lipid could be maximized when the xylose, peptone and Ca 2+ concentration was 61 g/L, 4.31 g/L, 0.67 mmol/L. C16 and C18 fatty acid account for about 91% of the total fatty acids. The most abundant fatty acid was oleic acid (42.68%), followed by palmitic acid (29.7%) and stearic acid (13.87%). The addition of Ca 2+ increased the content of unsaturated fatty acids (such as C16:1 and C18:1) and improved the unsaturation of fatty acids. Quantitative real time PCR analysis revealed that expression of genes related to lipid biosynthesis showed up-regulated by Ca 2+ treatment. This study provided a strategy for increase in lipid production and content of unsaturated fatty acids., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Aluminum (Al) toxicity is a major factor that limits crop productivity in acid soils. The toxic effects of Al exposure on Al-tolerant Cryptococcus humicola were analyzed at the physiological level. The exposure to 20 mM Al led to a clear increase in malondialdehyde content and a significant decrease in the levels of protein carbonyls, suggesting that Al stress caused oxidative damage to membrane lipids but not to proteins. Suppression subtractive hybridization (SSH) results showed that when C. humicola was exposed to 20 mM Al, a total of 141 ESTs were differentially expressed. Of them, 27 had unknown functions and 48 were newly identified in this study. The genes with known functions were categorized into seven groups. The largest group was related to metabolism and energy, followed by protein synthesis and processing, cell structure, signal transduction and transcription, transporters, stress and defense. Reverse transcription (RT)-PCR analysis of certain genes was performed to confirm the reliability of the SSH data. Nine selected genes were upregulated by Al in a time-dependent manner. The potential functions of some genes involved in Al-tolerance were predicted and are discussed. The diversity of the putative functions of these genes indicates that Al stress results in a complex response in C. humicola.