Plant resistance inducer AMHA enhances antioxidant capacities to promote cold tolerance by regulating the upgrade of glutathione S-transferase in tea plant

Abstract

Plant resistance inducers represent an alternative strategy that mitigate stress-induced damage in plants. Previously, 2-Amino-3-methylhexanoic Acid (AMHA), a novel natural plant resistance inducer, was shown to significantly bolster cold tolerance, thermotolerance and pathogen resistance in plants. However, the intricate mechanisms underlying AMHA’s response to cold stress remain elusive. Thus, we investigated the physiological and transcriptomic analyses of AMHA pretreatment on tea plant to determine the substantial role of AMHA under cold stress. The results showed that pretreatment with 100 nM AMHA effectively mitigated the detrimental effects of cold stress on photosynthesis and growth. Furthermore, differentially expressed genes were identified through RNA-seq during pretreatment, cold stress, and 2 days (2 d) of recovery. These genes were mainly enriched in pathways related to flavonoid/anthocyanin, carotenoid, and ascorbic acid-glutathione (AsA-GSH) cycle, including GST (encoding glutathione S-transferase). Potential regulatory relationships between the identified genes and transcription factors were also established. Antisense oligodeoxynucleotide-silencing and overexpression experiments revealed that CsGSTU7 enhances cold resistance by maintaining redox homeostasis. In conclusion, our study suggests that antioxidant-related signal molecules play a critical role in the signal cascades and transcriptional regulation mediating AMHA-induced cold-stress resistance in tea plant.