Study of the early regulatory mechanism of the Pichia kudriavzevii-induced resistance response in cherry tomato fruits

Abstract

Inducing fruit resistance helps control postharvest diseases effectively. The early signal response plays a crucial role in the subsequent series of fruit resistance reactions. Pichia kudriavzevii was identified as the effective biological elictior for enhancing induced resistance of cherry tomato fruit in this study and the early response signal and its regulatory mechanism subsequently was investigated by RNA sequencing analysis and reverse transcription quantitative real-time PCR (RT-qPCR). Profile trend analysis revealed that, in the early stages of induction (0.5 h and 1 h), the genes related to fruit Ca²⁺ signalling (CML1, CDPK4, CIPK1, and GLR2.9), MAPK signalling (MPK9), the ethylene signalling pathway (ETR2 and EFR1B), and the phenylpropane biosynthesis pathway (PAL5 and 4CL6) respond first. Moreover, the transcription of glutathione pathway genes (GSTU7 and HSP26-A) was upregulated to maintain the balance of reactive oxygen species (ROS) in fruits. After 24 h of induction by P. kudriavzevii, secondary metabolites such as lignin and terpenes in the phenylpropanoid biosynthesis pathway (4CL2, 4CL6, CCOAOMT, HMG2, and FPS1), as well as salicylic acid (SA), jasmonic acid (JA), and brassinosteroid (BR) signalling pathways in the plant hormone signalling pathway (TGA1A, TGA9, GH3.5, BAK1, CURL1), were activated. Additionally, upstream genes (PAL5 and 4CL6) in the phenylpropanoid pathway directly activate downstream gene transcription, promoting the production of resistance-related metabolites. P. kudriavzevii induces the activation of early signals such as Ca²⁺ signalling, MAPK signalling, and ethylene signalling, which in turn promote the activation of secondary metabolism and JA, BR, and SA hormone signalling in fruits to regulate resistance responses in fruits.