Combined high light and heat stress (HL + HS) causes more severe damage to the photosynthetic apparatus in plants than either high light (HL) or heat stress (HS) alone and drastically diminishes plant survival rates. Plants adapt to HL + HS stress by upregulating endogenous jasmonic acid (JA) levels. However, the pathways regulating this elevation and the signaling transduction to adapt to HL + HS remain unknown. Here, we identified the key gene sulfotransferase 2A (SlST2A) involved in JA metabolism and the upstream transcription factor heat shock factor B2b (SlHSFB2b) through transcriptome analysis and biochemical experiments. Under HL + HS conditions, SlHSFB2b expression was enhanced in tomato (Solanum lycopersicum); this suppressed SlST2A transcription, inhibiting JA catabolism and promoting the accumulation of endogenous JA. The elevated JA activated a transcriptional cascade orchestrated by SlMYC2, regulating transcription factors SlZF2 and SlDREB2A, as well as functional genes such as SlSAP7, SlBAG2, and SlPDX1.2, thereby enhancing tomato tolerance to HL + HS. Our findings provide insights into the mechanistic basis of endogenous JA upregulation and the complex response network mediated by JA under HL + HS stress in plants.

The Xishuangbanna (XIS) cucumber (Cucumis sativus var. xishuangbannanesis) is a semiwild variety that has many distinct agronomic traits. Here, long -reads generated by Nanopore sequencing technology helped assembling a high-quality genome (contig N50 = 8.7 Mb) of landrace XIS49. A total of 10,036 structural/sequence variations (SVs) were identified when comparing with Chinese Long (CL), and known SVs controlling spines, tubercles, and carpel number were confirmed in XIS49 genome. Two QTLs of hypocotyl elongation under low light, SH3.1 and SH6.1 were fine-mapped using introgression lines (donor parent, XIS49; recurrent parent, CL). SH3.1 encodes a red-light receptor Phytochrome B (PhyB, CsaV3_3G015190). An ∼4 kb large deletion (DEL) and highly divergent regions (HDRs) were identified in the promoter of the PhyB gene in XIS49. Loss of function of this PhyB caused a super-long hypocotyl phenotype. SH6.1 encodes a CCCH-type zinc finger protein FRIGIDA-ESSENTIAL LIKE (FEL, CsaV3_6G050300). FEL negatively regulated hypocotyl elongation but it was transcriptionally suppressed by a long terminal repeats (LTRs) retrotransposon insertion in CL cucumber. Mechanistically, FEL physically binds to the promoter of CONSTITUTIVE PHOTOMORPHOGENIC 1a (COP1a), regulating the expression of COP1a and the downstream hypocotyl elongation. These above results demonstrate the genetic mechanism of cucumber hypocotyl elongation under low light.

Drought stress profoundly impacts plant productivity worldwide. The roles of basic helix–loop–helix (bHLH) transcription factors are critical in processes of plant growth, development, and stress management. However, roles of specific bHLH genes in tomato, particularly in relation to drought tolerance, remain poorly understood. This research identified SlbHLH70 as a factor that enhances drought tolerance in tomato. Transgenic lines overexpressing SlbHLH70 exhibited enhanced drought tolerance and improved post-stress recovery, whereas SlbHLH70 knockout mutants showed increased sensitivity to drought stress. Further study showed that SlbHLH70 directly regulated genes associated with abscisic acid (ABA) synthesis, ABA-mediated signal transduction, and root development. Our research identified SlbHLH70 as an important regulator of drought resistance in tomato, offering a valuable genetic target for enhancing crop resilience to water shortages.

Malate transporters play pivotal roles in plant aluminum tolerance mechanisms. In the classic aluminum tolerance pathway, Al ³⁺ induces ALMT , which promotes malate exudation to chelate Al ³⁺ to enhance aluminum tolerance. However, in tomato, SlALMT was inhibited by Al ³⁺ , but Al ³⁺ still induced malate exudation. We found that SlSLAH2, upon induction by Al ³⁺ , can transport malate and is required for full activation of malate exudation by Al ³⁺ stress. SlWRKY37 contributes to SlSLAH2 induction by Al ³⁺ . Moreover, SlSLAH2 is phosphorylated in response to Al ³⁺ . We identify SlCDPK21 and SlPP2C72 as putative upstream kinase and phosphatase that could potentially facilitate phosphorylation homeostasis. SlCDPK21 can interact with SlSLAH2 in a heterologous system, phosphorylate SlSLAH2 at Thr167 in vitro and is also required for full malate exudation. SlPP2C72 can dephosphorylate SlSLAH2 in vitro and knock-out leads to increased malate exudation. Furthermore, Al ³⁺ downregulated SlPP2C72 , and Al ³⁺ treated seedling extracts can suppress SlPP2C72 phosphatase activity. We propose a synergistic transcription-phosphorylation cascade that can ensure a robust malate exudation across Al ³⁺ environments.

One key post-transcriptional modification mechanism that dynamically controls a number of physiological processes in plants is alternative splicing (AS). However, the functional impacts of AS on fruit ripening remain unclear. In this research, we used RNA-seq data from climacteric (VED, Harukei 3) and non-climacteric (PI, PS) melon cultivars to explore alternative splicing (AS) in immature and mature fruit. The results revealed dramatic changes in differential AS genes (DAG) between the young and mature fruit stages, particularly in genes involved in fruit development/ripening, carotenoid and capsaicinoid biosynthesis, and starch and sucrose metabolism. Serine/arginine-rich (SR) family proteins are known as important splicing factors in AS events. From the melon genome, a total of 17 SR members were discovered in this study. These genes could be classified into eight distinct subfamilies based on gene structure and conserved motifs. Promoter analysis detected various cis-acting regulatory elements involved in hormone pathways and fruit development. Interestingly, these SR genes exhibited specific expression patterns in reproductive organs such as flowers and ovaries. Additionally, concurrent with the increase in AS levels in ripening fruit, the transcripts of these SR genes were activated during fruit maturation in both climacteric and non-climacteric melon varieties. We also found that most SR genes were under selection during domestication. These results represent a novel finding of increased AS levels and SR gene expression during fruit ripening, indicating that alternative splicing may play a role in fruit maturation.