Cloning, Expression Analysis, and Functional Characterization of the NAC Transcription Factor SlNAC2-like from Tomato

To investigate the regulatory function of the tomato NAC transcription factor SlNAC2-like under high-temperature stress, the high-temperature-tolerant line Hm 2-2 and the high-temperature-sensitive line BY 1-2 were used as experimental materials. The SlNAC2-like gene was cloned from tomato leaves via reverse transcription PCR (RT-PCR), and its encoded protein was characterized using bioinformatics tools, phylogenetic analysis, and expression profiling. Subcellular localization and yeast self-activation assays were performed to determine protein localization and transcriptional activity. Virus-induced gene silencing (VIGS) was employed to generate SlNAC2-like-silenced plants, and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as proline (Pro) and malondialdehyde (MDA) contents, were measured under high-temperature stress using spectrophotometry. The results showed that the SlNAC2-like cDNA fragment was 1044 bp in length, with an 876 bp open reading frame encoding 291 amino acids containing a highly conserved NAM domain. The protein was localized in the nucleus and exhibited transcriptional activation activity. Quantitative real-time PCR (qRT-PCR) analysis revealed that SlNAC2-like expression was tissue-specific and induced by high temperature (42 °C), abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA). Silencing of SlNAC2-like compromised tomato high-temperature tolerance, as evidenced by reduced SOD, POD, and CAT activities, decreased Pro content, and a marked increase in MDA content, along with significant downregulation of genes involved in ABA, SA, and jasmonic acid (JA) signaling pathways. Collectively, these findings suggest that SlNAC2-like acts as a positive regulator of tomato tolerance to high-temperature stress and that its function is associated with antioxidant defense and the ABA, SA, and JA signaling pathways. However, the present study does not establish how SlNAC2-like regulates ROS homeostasis or hormone signaling, and identification of its direct target genes and interacting partners requires further experimental validation. This study provides valuable genetic resources and a theoretical basis for molecular breeding of stress-resistant tomato varieties.