Seed Priming with MeJa Prevents Salt-Induced Growth Inhibition and Oxidative Damage in Sorghum bicolor by Inducing the Expression of Jasmonic Acid Biosynthesis Genes

Genome-wide identification of the AP2/ERF gene family from Limonium bicolor and functional characterization of LbAP2/ERF32 under salt stress

AP2/ERF transcription factors (TFs) play important roles in plant growth and development, plant morphogenesis and response to environmental stresses. However, their biological roles in recretohalophytes are still not fully revealed. Limonium bicolor L. is a typical recretohalophyte, which secretes excessive salt ions through the salt glands on the epidermis. Here, 64 LbAP2/ERF genes were identified in L. bicolor genome, which were unevenly distributed on the eight chromosomes. Cis-elements related to growth and development, stress response and phytohormone response are distributed in multiple LbAP2/ERF promoters. Expression analysis indicated that LbAP2/ERF genes responsed to NaCl, PEG and ABA. And the salt gland density, salt secretion of leaves and overall salt tolerance of LbAP2/ERF32 silenced lines were significantly reduced. In agreement, the genes related to salt gland development and ion transport were significantly changed in LbAP2/ERF32-silenced lines. Our findings provided fundamental information on the structure and evolutionary relationship of LbAP2/ERF gene family in salt gland development and salt secretion of L. bicolor and gave theoretical guideline for further functional study of LbAP2/ERF genes in response to abiotic stress.

Heat shock protein HvHSP16.9 from wild barley enhances tolerance to salt stress

Heat shock proteins (HSPs) are known to play a crucial role in the response of plants to environmental stress, particularly heat stress. Nevertheless, the function of HSPs in salt stress tolerance in plants, especially in barley, remains largely unexplored. Here, we aimed to investigate and compare the salt tolerance mechanisms between wild barley EC_S1 and cultivated barley RGT Planet through a comprehensive analysis of physiological parameters and transcriptomic profiles. Results demonstrated that the number of differentially expressed genes (DEGs) in EC_S1 was significantly higher than in RGT Planet, indicating that wild barley gene regulation is more adaptive to salt stress. KEGG enrichment analysis revealed that DEGs were mainly enriched in the processes of photosynthesis, plant hormone signal transduction, and reactive oxygen species metabolism. Furthermore, the application of weighted gene correlation network analysis (WGCNA) enabled the identification of a set of key genes, including small heat shock protein (sHSP), Calmodulin-like proteins (CML), and protein phosphatases 2C (PP2C). Subsequently, a novel sHSP gene, HvHSP16.9 encoding a protein of 16.9 kDa, was cloned from wild barley, and its role in plant response to salt stress was elucidated. In Arabidopsis, overexpression of HvHSP16.9 increased the salt tolerance. Meanwhile, barley stripe mosaic virus-induced gene silencing (BSMV-VIGS) of HvHSP16.9 significantly reduced the salt tolerance in wild barley. Overall, this study offers a new theoretical framework for comprehending the tolerance and adaptation mechanisms of wild barley under salt stress. It provides valuable insights into the salt tolerance function of HSP, and identifies new candidate genes for enhancing cultivated barley varieties.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01455-4.

Methyl jasmonate improves selenium tolerance via regulating ROS signalling, hormonal crosstalk and phenylpropanoid pathway in Plantago ovata

Selenium (Se) toxicity is an emerging contaminant of global concern. It is known to cause oxidative stress, affecting plant growth and yield. Plantago ovata, a major cash crop known for its medicinal properties, is often cultivated in Se-contaminated soil. Thus, the aim of this study was to evaluate the use of methyl jasmonate (MeJA) seed priming technique to mitigate Se-induced phytotoxicity. The results demonstrated that Se stress inhibited P. ovata growth, biomass and lowered chlorophyll content in a dose-dependent manner. Treatment with 1 μM MeJA enhanced the antioxidant defence system via ROS signalling and upregulated key enzymes of phenylpropanoid pathway, PAL (1.9 times) and CHI (5.4 times) in comparison to control. Caffeic acid, Vanillic acid, Chlorogenic acid, Coumaric acid and Luteoloside were the most abundant polyphenols. Enzymatic antioxidants involved in ROS scavenging, such as CAT (up to 1.3 times) and GPOX (up to 1.4 times) were raised, while SOD (by 0.6 times) was reduced. There was an upregulation of growth-inducible hormones, IAA (up to 2.1 fold) and GA (up to 1.5 fold) whereas, the stress-responsive hormones ABA (by 0.6 fold) and SA (by 0.5 fold) were downregulated. The alleviation of Se toxicity was also evident from the decrease in H2O2 and MDA contents under MeJA treatment. These findings suggest that MeJA can effectively improve Se tolerance and nutraceutical value in P. ovata by modulating the phytohormone regulatory network, redox homeostasis and elicits accumulation of polyphenols. Therefore, MeJA seed priming could be an efficient way to enhance stress resilience and sustainable crop production.

Carbon Monoxide Alleviates Salt-Induced Oxidative Damage in Sorghum bicolor by Inducing the Expression of Proline Biosynthesis and Antioxidant Genes

Crop growth and yield are affected by salinity, which causes oxidative damage to plant cells. Plants respond to salinity by maintaining cellular osmotic balance, regulating ion transport, and enhancing the expression of stress-responsive genes, thereby inducing tolerance. As a byproduct of heme oxygenase (HO)-mediated degradation of heme, carbon monoxide (CO) regulates plant responses to salinity. This study investigated a CO-mediated salt stress tolerance mechanism in sorghum seedlings during germination. Sorghum seeds were germinated in the presence of 250 mM NaCl only, or in combination with a CO donor (1 and 1.5 μM hematin), HO inhibitor (5 and 10 μM zinc protoporphyrin IX; ZnPPIX), and hemoglobin (0.1 g/L Hb). Salt stress decreased the germination index (47.73%) and root length (74.31%), while hydrogen peroxide (H2O2) (193.5%), and proline (475%) contents increased. This increase correlated with induced HO (137.68%) activity and transcripts of ion-exchanger and antioxidant genes. Salt stress modified vascular bundle structure, increased metaxylem pit size (42.2%) and the Na+/K+ ratio (2.06) and altered primary and secondary metabolites. However, exogenous CO (1 μM hematin) increased the germination index (63.01%) and root length (150.59%), while H2O2 (21.94%) content decreased under salt stress. Carbon monoxide further increased proline (147.62%), restored the vascular bundle structure, decreased the metaxylem pit size (31.2%) and Na+/K+ ratio (1.46), and attenuated changes observed on primary and secondary metabolites under salt stress. Carbon monoxide increased HO activity (30.49%), protein content, and antioxidant gene transcripts. The alleviatory role of CO was abolished by Hb, whereas HO activity was slightly inhibited by ZnPPIX under salt stress. These results suggest that CO elicited salt stress tolerance by reducing oxidative damage through osmotic adjustment and by regulating the expression of HO1 and the ion exchanger and antioxidant transcripts.

Caffeic Acid O-Methyltransferase Gene Family in Mango (Mangifera indica L.) with Transcriptional Analysis under Biotic and Abiotic Stresses and the Role of MiCOMT1 in Salt Tolerance

Caffeic acid O-methyltransferase (COMT) participates in various physiological activities in plants, such as positive responses to abiotic stresses and the signal transduction of phytohormones. In this study, 18 COMT genes were identified in the chromosome-level reference genome of mango, named MiCOMTs. A phylogenetic tree containing nine groups (I-IX) was constructed based on the amino acid sequences of the 71 COMT proteins from seven species. The phylogenetic tree indicated that the members of the MiCOMTs could be divided into four groups. Quantitative real-time PCR showed that all MiCOMT genes have particularly high expression levels during flowering. The expression levels of MiCOMTs were different under abiotic and biotic stresses, including salt and stimulated drought stresses, ABA and SA treatment, as well as Xanthomonas campestris pv. mangiferaeindicae and Colletotrichum gloeosporioides infection, respectively. Among them, the expression level of MiCOMT1 was significantly up-regulated at 6-72 h after salt and stimulated drought stresses. The results of gene function analysis via the transient overexpression of the MiCOMT1 gene in Nicotiana benthamiana showed that the MiCOMT1 gene can promote the accumulation of ABA and MeJA, and improve the salt tolerance of mango. These results are beneficial to future researchers aiming to understand the biological functions and molecular mechanisms of MiCOMT genes.