Genome-wide identification of SnRK gene family and functional characterization of AcSnRK2.4 in response to heat stress in kiwifruit

Abstract

Sucrose non-fermenting 1-related protein kinases (SnRKs) are pivotal in the plant’s response to biotic and abiotic stresses, primarily by triggering protein phosphorylation cascades. Despite their significance, there is a paucity of information regarding SnRK genes within the kiwifruit (Actinidia chinensis). In this study, 51 AcSnRK genes were identified from kiwifruit genome and distributed on 23 chromosomes. Phylogenetic analysis showed that all AcSnRKs were classified into 3 subfamilies. The gene structure, conserved motif, gene duplications and cis-acting element in the promoter were accomplished using TBtools-II software. The publicly available transcriptome datasets and qRT-PCR analysis revealed that the majority of AcSnRKs were down-regulated by heat stress, with AcSnRK2.4 demonstrating a particularly pronounced reduction in expression. In addition, we explored the biological function of AcSnRKs2.4 using transient transformation methods. Overexpressed of AcSnRKs2.4 showed higher SPAD, but lower malondialdehyde (MDA) content, relative electrolyte leakage (EL) and ROS content compared with OE-EV lines under heat stress; while suppression of AcSnRKs2.4 showed a opposite result. Furthermore, OE-AcSnRK2.4 lines exhibited higher photosynthetic fluorescence parameters (except for Y(NO)), while these parameters were lower in pTRV-AcSnRK2.4 plants. These findings suggest that AcSnRK2.4 positively regulates kiwifruit's response to heat stress. Our findings offer a new insight into the potential function of AcSnRK2.4 in abiotic stresses and provide a theoretical groundwork for the molecular mechanisms underlying kiwifruit adaptation to such stress.