Kai Zhao

Key message SlASIL2 can regulate tomato heat tolerance by suppressing the expression of SlHSP20/SlHSP90 and forming protein complexes with SlDREBA4. Abstract Tomato (Solanum lycopersicum) is an important vegetable crop with substantial economic value. High-temperature stress severely impacts tomato yield and quality, making it a major constraint on the development of the tomato industry. The DREBA4 transcription factor is thought to play a key role in the high-temperature stress response pathway; however, its regulatory mechanism remains to be fully elucidated. In this study, a combination of genetic and biochemical approaches was used to elucidate the roles of SlDREBA4 and SlASIL2 in regulating the transcription of SlHSP20 and SlHSP90. Further analysis were performed to investigate the function of the SlASIL2 gene using overexpression and silencing systems. Additionally, SlASIL2 was found to suppress the reactive oxygen species (ROS) scavenging system, thereby negatively regulating tomato heat tolerance. Moreover, SlASIL2 directly binds to the promoters of SlHSP20 and SlHSP90, repressing their expression and thereby reducing tomato heat tolerance. Importantly, the interaction between SlDREBA4 and SlASIL2 mitigated the inhibitory effect of SlASIL2 on SlHSP20 and SlHSP90, contributing to the establishment of a stable physiological state in tomatoes under high-temperature conditions. These results indicate that the transcriptional regulation of SlHSP20 and SlHSP90 by SlDREBA4 and SlASIL2, together with the modulation of the ROS scavenging system, collectively fine-tune the tomato response to short-term heat stress. Our findings further expand the understanding of the molecular regulatory network involved in plant heat stress responses.

Chrysanthemum is one of the world’s four main cut flowers. However, postharvest drought stress severely disrupts water homeostasis, triggering reactive oxygen species burst and membrane lipid peroxidation, thereby reducing its ornamental quality and vase life. Melatonin serves as a multifunctional antioxidant and stress regulator. This study demonstrated that 200 μmol L⁻¹ melatonin effectively alleviated drought-induced leaf wilting, maintained relative water content, decreased the accumulation of MDA, H₂O₂, and O₂^•−, and enhanced the activities of SOD, CAT, POD, and APX. Concurrently, non-enzymatic antioxidants (proline, GSH, ASA) accumulated to high levels. RNA-seq analysis revealed that drought affects pathways closely related to the production of antioxidant and osmoprotectant metabolites, while melatonin initiated extensive transcriptional reprogramming and responded to drought stress through distinct pathways at the early (12 h) and late (24 h) treatment stages. Melatonin also modulated key transcription factor families, including bHLH, NAC, ERF, MYB, and bZIP. Collectively, exogenous MT mitigates drought damage in chrysanthemum cut flowers by coordinating antioxidant systems and complex transcriptional regulatory networks. This study provides a theoretical foundation for improving postharvest drought tolerance and prolonging the vase life of cut flowers.

High-temperature stress severely limits the growth, development, and productivity of tomatoes. Understanding the molecular mechanisms underlying its thermotolerance is crucial for breeding heat-resistant varieties. This study employed a stepwise experimental strategy to systematically elucidate the role of the chlorophyll a/b-binding protein SlCAB3 in tomato thermotolerance. First, a high-temperature responsive transcription factor, SlDREBA4, previously identified in our lab, was used in a yeast two-hybrid screen to identify potential interacting proteins, including SlCAB3. The interaction between SlDREBA4 and SlCAB3 was further validated using tobacco in vivo luciferase complementation imaging (LCI) and in vitro pull-down assays. Subsequently, the expression patterns of SlCAB3 under heat stress were analyzed, and its biological function was further evaluated through overexpression, gene silencing, and knockout experiments. Additionally, reactive oxygen species (ROS) accumulation, antioxidant enzyme activities, chlorophyll content, and the expression of stress-responsive genes were measured to comprehensively assess their physiological and molecular regulatory roles. The results indicate that SlCAB3 encodes a typical chlorophyll a/b-binding protein and is rapidly induced by heat stress. Overexpression of SlCAB3 significantly enhances plant thermotolerance, evidenced by reduced heat damage, increased chlorophyll content, decreased ROS accumulation, elevated antioxidant enzyme activities, and upregulation of antioxidant-related genes. Conversely, silencing SlCAB3 produces opposite effects. Moreover, co-expression of SlCAB3 with SlDREBA4 further improves thermotolerance, accompanied by enhanced expression of heat shock protein-related and antioxidant-related genes. In conclusion, SlCAB3 is a positive regulator of tomato thermotolerance, and the interaction module formed with SlDREBA4 may collectively enhance heat resistance by strengthening antioxidant defense and heat stress response mechanisms.

(1) Background: The bHLH (basic helix-loop-helix) transcription factor family is one of the most abundant in plants and is involved in plant growth, development, and abiotic stress responses. Notably, the functions of most bHLH family members remain poorly characterized. (2) Results: CmbHLH112, a nuclear-localized bHLH transcription factor from chrysanthemum, exhibits transcriptional activation activity. Overexpression of CmbHLH112 in Arabidopsis significantly promotes flowering and enhances drought resistance. qRT-PCR analysis revealed that CmbHLH112 regulates flowering time by affecting the expression of key flowering genes, including FT, SOC1, LFY, and FLC. Under drought stress, CmbHLH112 overexpression plants showed reduced ROS accumulation compared with wild-type plants, accompanied by elevated activities of key antioxidant enzymes and increased proline content. Moreover, transgenic plants exhibited lower MDA concentrations and reduced water loss rates under drought conditions, further indicating enhanced stress resilience. Overexpression of CmbHLH112 also upregulates ABA levels under drought stress, while simultaneously promoting the expression of genes involved in ABA biosynthesis and ABA signaling pathways. (3) Conclusions: Our results demonstrate that heterologous overexpression of CmbHLH112 in Arabidopsis enhances drought tolerance and promotes flowering. Thus, CmbHLH112 is proposed to play a dual role in modulating flowering time and drought tolerance, at least partly by regulating ABA biosynthesis.

The homeodomain–leucine zipper (HD-zip) gene family plays a crucial role in plant development and stress responses. However, systematic identification studies of this gene family in eggplant are still lacking. In this study, we systematically identified 44 HD-zip genes in the eggplant genome database using bioinformatics methods and analyzed their expression levels under light and multiple hormones by RT-qPCR. The results show that members of the SmHD-zip gene family were classified into four groups (HD-zip I, II, III, and IV) based on the phylogenetic relationship. Cis-acting elements related to plant development, hormones, and stress were identified in the promoter regions of the SmHD-zip gene family. Furthermore, the expression of the SmHDZ2 gene was upregulated during the fruit development stage, while nine SmHD-zip genes exhibited downregulated expression patterns. Notably, some SmHD-zip genes were identified as key regulators of eggplant responses to light and multiple hormone signals. Overall, these findings not only provide valuable insights into the evolutionary and functional characteristics of eggplant HD-Zips but also suggest that HD-zip genes likely play a significant role in regulating fruit development and ripening by integrating light and multiple hormone signaling pathways. Therefore, this study laid the foundation for further research on eggplant quality.

Anthocyanins are important flavonoid compounds in plants that are associated with the color formation and antioxidant activity of flowers, fruits, and other organs. Ultraviolet B radiation (UV-B) is one of the key environmental factors that influence anthocyanin accumulation in plants and HY5 is involved in plant photomorphogenesis. However, the molecular mechanism of the signal network of UV-B regulating anthocyanin biosynthesis in capsicum via HY5 remains unclear. In this study, we identified the transcription factor CaHY5, which mediates UV-B signaling, and demonstrated its regulatory role in anthocyanin biosynthesis in purple pepper (Capsicum annuum L.). The results showed that there were photoresponsive and hormone-responsive elements on the CaHY5 promoter that responded to UV-B, indoleacetic acid, salicylic acid, 6-benzyladenine, abscisic acid, and melatonin treatments. UV-B treatment induced the expression of CaHY5 and anthocyanin structural genes. CaHY5 gene-silenced positive plants showed different degrees of the yellowing phenomenon, which affected the expression of the anthocyanin biosynthesis structural gene. The expression levels of anthocyanin biosynthesis-related genes in CaHY5-silenced positive plants increased considerably. This study provides insights into the role of CaHY5 in UV-B-induced anthocyanin biosynthesis in purple pepper.

GATA proteins are transcription factors of zinc finger proteins, which play an important role in plant growth development and abiotic stress. However, there have been no identification or systematic studies of the GATA gene family in eggplant. In this study, 28 SmGATA genes were identified in the genome database of eggplant, which could be divided into four subgroups. Plant development, hormones, and stress-related cis-acting elements were identified in promoter regions of the SmGATA gene family. RT-qPCR indicated that 4 SmGATA genes displayed upregulated expressions during fruit developmental stage, whereas 2 SmGATA genes were down-regulated expression patterns. It was also demonstrated that SmGATA genes may be involved in light signals to regulate fruit anthocyanin biosynthesis. Furthermore, the expression patterns of SmGATA genes under ABA, GA and MeJA treatments showed that the SmGATAs were involved in the process of fruit ripening. Notably, SmGATA4 and SmGATA23 were highly correlated with the expression of anthocyanin biosynthesis genes, light-responsive genes, and genes that function in multiple hormone signaling pathways and the proteins they encoded were localized in the nucleus. All these results showed GATA genes likely play a major role in regulating fruit anthocyanin biosynthesis by integrating the light, ABA, GA and MeJA signaling pathways and provided references for further research on fruit quality in eggplant.

Carotenoids are important pigments in pepper fruits. The colors of each pepper are mainly determined by the composition and content of carotenoid. The ‘ZY’ variety, which has yellow fruit, is a natural mutant derived from a branch mutant of ‘ZR’ with different colors. ZY and ZR exhibit obvious differences in fruit color, but no other obvious differences in other traits. To investigate the main reasons for the formation of different colored pepper fruits, transcriptome and metabolome analyses were performed in three developmental stages (S1–S3) in two cultivars. The results revealed that these structural genes (PSY1, CRTISO, CCD1, CYP97C1, VDE1, CCS, NCED1 and NCED2) related to carotenoid biosynthesis were expressed differentially in the two cultivars. Capsanthin and capsorubin mainly accumulated in ZR and were almost non-existent in ZY. S2 is the fruit color-changing stage; this may be a critical period for the development of different color formation of ZY and ZR. A combination of transcriptome and metabolome analyses indicated that CCS, NCED2, AAO4, VDE1 and CYP97C1 genes were key to the differences in the total carotenoid content. These new insights into pepper fruit coloration may help to improve fruit breeding strategies.