Table 3.

Summary of key transcriptomics, proteomics, and metabolomics studies under high-temperature stress in some vegetable crops

Species	Stress condition	Specific tissue	Approach	Functional annotation method	Key findings	References
Transcriptomics
Capsicum annuum L	42 °C for 3 d	Seedlings	RNA-Seq	GO, KEGG	11,633 DEGs were identified 38 heat shock factors (Hsps), 17 HS transcription factors (Hsfs), 38 NAC (NAM, ATAF1/2, and CUC2), and 35 WRKY proteins that were responsive to HS	Wang et al. (2021a)
Capsicum annuum	40 °C	Leaves	RNA-Seq	GO	12,494 DEGs were identified. Identified DEGs to provide various stimuli for developing HS resistant cultivars	Kang et al. (2020)
Solanum melongena L	38 °C and 43 °C for 3 h	Leaves	RNA-Seq	GO, KEGG	3067 and 1456 DEGs were identified. 315 and 342 genes were upregulated and downregulated DEGs involved in antioxidant enzyme systems, detoxication, phytohormones, and transcription factors	Zhang et al. (2020)
Benincasa hispida	45 °C/40 °C in day/night for 5 d	Leaves	RNA-Seq	GO, KEGG	1505 DEGs (914 upregulated and 591 downregulated) were identified DEGs are related to heat shock proteins (HSPs), ubiquitin-protein ligase, transcriptional factors, and pentatricopeptide repeat-containing proteins	Wang et al. (2019c)
Solanum melongena L	45 °C for 6 h	Fruits	RNA-Seq	GO, KEGG	770 DEGs were identified 16 genes related to anthocyanin biosynthesis	Zhang et al. (2019)
Proteomics
Brassica juncea	30 °C	Sprout	Acetonitrile	LC–MS/MS, UPLC, UNIPROT, and KEGG	172 DEPs identified. Increased expression of genes/ proteins related to melatonin, electrolyte leakage, GSH, and POD. Increased defense pressure, protein biosynthesis, signal transduction, and transcription under HS. Involved in protein transport	Cheng et al. (2020)
Brassica campestris L	40/30 °C for 3 d	Leaf	acetate–methanol	HPLC, LC–MS/MS	1022 DEPs were identified Increased expression of genes/ proteins related to redox homeostasis, photosynthesis, carbohydrate metabolism, heat-shock protein, and chaperones and signal transduction pathways	Yuan et al. (2019)
Spinacia oleracea L	37/32 °C day/night	Leaves	Phenol	iTRAQ, LC–MS/MS	911 DEPs were identified related to ROS homeostasis, endomembrane trafficking, and cross-membrane transport pathways	Zhao et al. (2018a, b)
Cucumis sativus	42 °C for 7d	Leaves	acetone	MALDI-TOF/TOF MS, 2-DE	77 DEPs identified involved photosynthesis, energy and metabolism, defense response, and protein and nucleic acid biosynthesis	Xu et al. (2018)
Lactuca sativa L	33 °C	Stems	TCA/acetone	iTRAQ, LC, ESI, MS/MS	5454 DEP identified 619 proteins induced by HS and associated with photosynthesis and tryptophan metabolism involved in IAA biosynthesis	Hao et al. (2018)
Metabolomics
Lactuca sativa L	35 ◦C for 40 h	Leaves	GC–MS, UPLC-IMS-QTOF/MS	PCA	Increased accumulation of organic acids, amino acids, terpenoids, phenolic compounds, carbohydrates, and lipids are involved in lettuce seed germination and thermo-inhibition	Wei et al. (2020)
Sargassum fusiforme	32 °C for 7 d	Leaves	GC–MS	OPLS-DA, PCA, KEGG	A heat shock increases the production of organic acids, amino acids, sugars or sugar alcohols, esters, and amines Changes in metabolic pathways may contribute to the HS tolerance	Liu and Lin (2020)
Capsicum annuum L	~ 40 °C for 28 h	Leaves	LC–ESI–MS/MS, ESI-Q TRAP-MS/MS	PLS-DA, PCA, KEGG	94 and 108 differentially accumulated metabolites (DAMs) were identified Amino acids, organic acids, flavonoids, and sugars are involved in HS tolerance	Wang et al. (2019a)
Solanum lycopersicum	40 °C/30 °C (day/night) over a 48 h	Fruits	GC–MS	PCA, UPLC-PDA	Increased accumulation of threonine and β-sitosterol levels. Proline and GABA responsive to HS	Almeida et al. (2021)
Solanum lycopersicum	38 °C for 1 h	Leaves	GC-TOF–MS, LC-QTOF-MS	PCA	Increased accumulation of sucrose, glucose, putrescine, and caffeoyl quinic acid isomers involved in HS tolerance	Paupière et al. (2020)