Plants have evolved a sophisticated chemical defense network to counteract pathogens, with phenolamides and salicylic acid (SA) playing pivotal roles in the immune response. However, the synergistic regulatory mechanisms of their biosynthesis remain to be explored. Here, we identified a biosynthetic gene cluster on chromosome 2 (BGC2) associated with the biosynthesis of phenolamide and SA, wherein the key component SlEPS1 exhibits dual catalytic functions for the synthesis of phenolamides and SA. Overexpression of the key component SlEPS1 of BGC2 in tomato enhanced resistance to the bacterial pathogen Pst DC3000, whereas knockout plants were more susceptible. Exogenous applications of SA and phenolamides revealed that these two compounds act synergistically to enhance plant resistance. Notably, during tomato domestication, a disease‐resistant allele of SlEPS1, SlEPS1^HapB, was subject to negative selection, leading to a reduction in phenolamide and SA levels and compromised disease resistance in modern varieties. Moreover, the SlMYB78 directly regulates the BGC2 gene cluster to enhance phenolamide and SA biosynthesis, modulating resistance to Pst DC3000. Our study employed multi‐omics approaches to describe the synergistic regulation of phenolamide and SA biosynthesis, offering new insights into the complexity of plant immune‐related metabolism.

Summary: Steroidal glycoalkaloids (SGAs) constitute a characteristic class of antinutritional metabolites that are found in certain Solanum species. Despite the considerable studies on SGA biosynthesis, the mechanisms of crosstalk between hormone signaling pathways that regulate SGA content still remain to be elucidated. Here, we performed a metabolic genome‐wide association study (mGWAS) based on the levels of SGA metabolites and identified SlERF.H6 as a negative regulator of bitter‐SGA biosynthesis. SlERF.H6 repressed the expression of SGA biosynthetic glycoalkaloid metabolism (GAME) genes and caused a subsequent decrease in the abundance of bitter SGAs. Furthermore, SlERF.H6 were shown to act downstream of GAME9, a regulator of SGA biosynthesis in tomato. We also uncovered the interplay between ethylene and gibberellin (GA) signaling in regulating SGA biosynthesis. SlERF.H6, acting as a downstream component in ethylene signaling, modulated GA content by inhibiting SlGA2ox12 expression. Increasing levels of endogenous GA₁₂ and GA₅₃ in SlERF.H6‐OE could inhibit of GA on SGA biosynthesis. Additionally, 1‐aminocyclopropane‐1‐carboxylic acid (ACC) treatment decreased the stability of SlERF.H6, weakening its inhibition on GAME genes and SlGA2ox12, and caused bitter‐SGA accumulation. Our findings reveal a key role of SlERF.H6 in the regulation of SGA biosynthesis through the coordinated ethylene‐gibberellin signaling.

Branched-chain amino acids (BCAAs) are essential amino acids in tomato (Solanum lycopersicum) required for protein synthesis, which also modulate growth and abiotic stress responses. To date, little is known about their uptake and transport in tomato especially under abiotic stress. Here, the tomato amino acid permease 6 (SlAAP6) gene was identified as an amino acid transporter that restored mutant yeast cell growth on media with a variety of amino acids, including BCAAs. Overexpression of SlAAP6 (SlAAP6-OE) in tomato raised the BCAA content and elevated the fresh weight, while SlAAP6 knockouts (slaap6) showed reduced levels of neutral and basic amino acids in seedling tissues and lower total free amino acid distribution to shoots. In comparison to wild type (WT) and slaap6 mutants, SlAAP6-OE alleviated root limited growth by elevated BCAA transport and upregulated the expression of root-growth-related genes by increasing BCAAs in vivo. As SlAAP6 serves as a positive regulator for BCAA abundance, SlAAP6-OE lines showed greater salinity tolerance, while slaap6 mutants exhibited increased salt sensitivity. The salt tolerance of SlAAP6-OE plants was further enhanced by the application of exogenous BCAAs. In addition, BCAA supplementation reduced the accumulation of H₂O₂ in root under salt stress conditions. Based on these findings, SlAAP6-mediated uptake and transport of BCAAs facilitated growth and salt tolerance in tomato. By characterizing this key amino acid transporter, this study provides a novel approach to simultaneously enhance tomato nutritional quality, growth and development, and stress resistance through genetic improvement.

Coconut is a tropical fruit whose flesh has high flavor quality and nutritional value; however, the differences between coconut varieties are still unclear. Here, volatiles and non-volatiles were profiled at three ripening stages by HS-SPME/GC-MS and UHPLC-MS/MS in two coconut varieties (Hainan Tall, HT and Green Dwarf, GD). Four metabolite classes of volatiles were associated with good aroma including hydrocarbons, benzenoids, alcohols and esters, and these volatiles were generally higher in GD, especially at 7 and 9 months of coconut growth. Pathway-based metabolomics revealed that flavonols and their derivatives were significantly enriched in HT, and some of these metabolites were key determinants of HT flesh bitterness, including kaempferol 7-O-glucoside, a known bitter metabolite. Despite the overall accumulation of amino acids, including L-alanine, L-serine and L-methionine in GD, comparative metabolomics revealed that HT flesh provides a higher content of vitamins than GD. This study sheds light on the metabolic pathways and key metabolites differentiating the flesh flavor quality and nutritional value among coconut varieties, and reveals the possible mechanisms of flavor formation and regulation in coconut fruits.