Transcriptional profiling reveals molecular basis and the role of arginine in response to low-pH stress in Pichia kudriavzevii

Abstract BackgroundThe non-conventional yeast Pichia kudriavzevii possesses a unique ability to tolerate various environmental stresses particularly low-pH stress. Thus, it is considered to be a promising biotechnological host for the production of various organic acids under low-pH conditions. However, little is known about the low-pH stress response in P. kudriavzevii, which significantly restricts its future development. ResultsIn this study, P. kudriavzevii JLY1107 showed great tolerance to low-pH stress, but its cell aggregation upon acidic conditions is unfavorable for the development of low-pH fermentation. To explore the molecular basis, we conducted RNA-Seq to compare global gene expression in response to low-pH. Among the 429 differentially expressed genes, the genes associated with regulation of membrane lipid composition, filamentous growth and arginine metabolism were selected for in-depth discussions. The up-regulation of genes associated with arginine uptake and degradation suggests a potential role of arginine in response to low-pH strsss. We therefore present data supporting the hypothesis that P. kudriavzevii maintains intracellular homeostasis by using the ammonia produced by arginine catabolism. Furthermore, external addition of arginine significantly enhances growth and reduces cell aggregation of P. kudriavzevii under low-pH conditions.ConclusionsArginine was demonstrated to be a promising molecule for improving cell growth and preventing cell aggregation under extremely low-pH conditions. Our study is a step towards developing the non-conventional yeast P. kudriavzevii as a platform host for the production of organic acids under low-pH conditions.