Genome-wide identification and genetic characterization of the CaMYB family and its response to five types of heavy metal stress in hot pepper (Capsicum annuum cv. CM334)

Identification and Characterization of Copper-Responsive miRNAs and Their Target Genes in Jerusalem Artichoke

microRNAs (miRNAs) are key regulators of gene expression in plants, significantly contributing to various biological processes and stress responses. While their roles have been extensively studied in Arabidopsis thaliana and other model plants, the response of miRNAs to copper (Cu) stress in Jerusalem artichoke remains unknown. This study addresses this gap by investigating Cu-responsive miRNAs and their regulatory roles in Jerusalem artichoke under Cu stress. Through small RNA library analysis, six miRNA families-miR168, miR394, miR397, miR398, miR408, and miR858-were identified in Cu-stressed and control plants of the Jerusalem artichoke cv. NY1. These miRNAs possess characteristic stem-loop precursor structures and detectable miRNA* sequences, with miR858 having unusually long precursors (1524-6448 nt). This study outlines a framework for miRNA-mediated Cu stress responses in Jerusalem artichoke, highlighting the roles of both well-established Cu-responsive miRNAs (miR397, miR398, and miR408) and other conserved miRNAs (miR168, miR394, and miR858). These miRNAs are suggested to influence Cu stress adaptation by modulating target genes involved in essential metabolic, physiological, and morphological processes, offering new insights into miRNA-mediated stress regulation in plants.

Cadmium accumulation potential and detoxication mechanism of Koenigia tortuosa: A novel extremely hardy plant from high altitude lead-zinc mine in Qinghai-Tibet Plateau

Hardy plants play a crucial role in restoring high-altitude tailings ponds, but the accumulation of potentially toxic elements (PTEs) and detoxification mechanisms in alpine plants are understudied. This study first investigated the cadmium (Cd) accumulation capacity and detoxification mechanisms by comparative transcriptomics with different Cd stress (0, 5, 10, 20 and 40 mg L-1 Cd2+) of Koenigia tortuosa from a lead-zinc mine (4950 m above sea level) in Qinghai-Tibet Plateau. The findings revealed that, despite elevated Cd concentrations suppressed the growth of Koenigia tortuosa, the plant retained a notable ability to accumulate Cd. The content of soluble protein and antioxidant enzyme activities increased with the concentration of Cd from 5 mg L-1 to 20 mg L-1, and then decreased when the concentration of Cd increased to 40 mg L-1. The maximum Cd accumulation in roots was 269.44 mg kg-1 at the 20 mg L-1 Cd concentration, with 61.83% of Cd extracted by NaCl. In addition, transcriptome analysis showed that differentially expressed genes (DEGs) were mainly distributed in the nucleotide metabolism, oxidative phosphorylation pathway, glutathione metabolism and plant signaling, which were significantly up-regulated in ribosomal protein genes, translational factor genes and glutathione-related genes. These results will contribute to revealing the physiological response and molecular mechanism of Cd tolerance in Koenigia tortuosa, supporting the ecological remediation of Cd contaminated sites in high-altitude mining areas.

Physiological and Genetic Aspects of Resistance to Abiotic Stresses in Capsicum Species

Abiotic stress is one of the key factors harming global agriculture today, seriously affecting the growth and yield of vegetables. Pepper is the most widely grown vegetable in the world, with both high nutritional and economic values. Currently, the increase in global extreme weather events has heightened the frequency of abiotic stresses, such as drought, high and low temperatures, waterlogging, and high salt levels, which impairs pepper growth and development, leading to its reduced yield and quality. In this review, we summarize the research progress on the responses of pepper to abiotic stress in recent years in terms of physiology, biochemistry, molecular level, and mitigation measures. We then explore the existing problems and propose future research directions. This work provides a reference for the cultivation and development of new pepper varieties resistant to abiotic stress.

The regulatory pathway of transcription factor MYB36 from Trichoderma asperellum Tas653 resistant to poplar leaf blight pathogen Alternaria alternata Aal004

In fungi, MYB transcription factors (TFs) mainly regulate growth, development, and resistance to stress. However, as major disease-resistance TFs, they have rarely been studied in biocontrol fungi. In this study, MYB36 of Trichoderma asperellum Tas653 (Ta) was shown to respond strongly to the stress caused by Alternaria alternata Aa1004. Compared with wild-type Ta (Ta-Wt), the inhibition rate of the MYB36 knockout strain (Ta-Kn) on Aa1004 decreased by 11.06%; the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities decreased by 82.15 U/g, 0.19 OD470/min/g, and 1631.2 μmol/min/g, respectively. The MYB36 overexpression strain (Ta-Oe) not only enhanced hyperparasitism on Aa1004, caused its hyphae to swell, deform, or even rupture, but also reduced the incidence rate of poplar leaf blight. MYB36 regulates downstream (TFs, detoxification genes, defense genes, and other antifungal-related genes by binding to the cis-acting elements "ACAT" and "ATCG". Zinc finger TFs, as the main antifungal TFs, account for 90% of the total TFs, and Zn37.5 (23.24-) and Zn83.7 (23.18-fold) showed the greatest expression difference when regulated directly by MYB36. The detoxification genes mainly comprised 11 major major facilitator superfamily (MFS) genes, among which MYB36 directly increased the expression levels of three genes by more than 2-3.44-fold. The defense genes mainly encoded cytochrome P450 (P450) and hydrolases. e.g., P45061.3 (2-10.95-), P45060.2 (2-7.07-), and Hyd44.6 (2-2.30-fold). This study revealed the molecular mechanism of MYB36 regulation of the resistance of T. asperellum to A. alternata and provides theoretical guidance for the biocontrol of poplar leaf blight and the anti-disease mechanism of biocontrol fungi.

Genetic response analysis of Beauveria bassiana Z1 under high concentration Cd(II) stress

Cadmium (Cd(II)) has carcinogenic and teratogenic toxicity, which can be accumulated in the human body through the food chain, endangering human health and life. In this study, a highly Cd(II)-tolerant fungus named Beauveria bassiana Z1 was studied, and its Cd(Ⅱ) removal efficiency was 71.2% when the Cd(II) concentration was 10 mM. Through bioanalysis and experimental verification of the transcriptome data, it was found that cadmium entered the cells through calcium ion channels, and then complexed with intracellular glutathione (GSH) and stored in vacuoles or excluded extracellular by ABC transporters. Cytochrome P450 was significantly upregulated in many pathways and actively participated in detoxification related reactions. The addition of cytochrome inhibitor taxifolin reduced the removal efficiency of Cd(II) by 45%. In the analysis, it demonstrated that ACOX1 gene and OPR gene of jasmonic acid (JA) synthesis pathway were significantly up-regulated, and were correlated with bZIP family transcription factors cpc-1_0 and pa p1_0. The results showed that exogenous JA could improve the removal efficiency of Cd(II) by strain Z1.

MYB transcription factors and their role in Medicinal plants

Transcription factors are multi-domain proteins that regulate gene expression in eukaryotic organisms. They are one of the largest families of proteins, which are structurally and functionally diverse. While there are transcription factors that are plant-specific, such as AP2/ERF, B3, NAC, SBP and WRKY, some transcription factors are present in both plants as well as other eukaryotic organisms. MYB transcription factors are widely distributed among all eukaryotes. In plants, the MYB transcription factors are involved in the regulation of numerous functions such as gene regulation in different metabolic pathways especially secondary metabolic pathways, regulation of different signalling pathways of plant hormones, regulation of genes involved in various developmental and morphological processes etc. Out of the thousands of MYB TFs that have been studied in plants, the majority of them have been studied in the model plants like Arabidopsis thaliana, Oryza sativa etc. The study of MYBs in other plants, especially medicinal plants, has been comparatively limited. But the increasing demand for medicinal plants for the production of biopharmaceuticals and important bioactive compounds has also increased the need to explore more number of these multifaceted transcription factors which play a significant role in the regulation of secondary metabolic pathways. These studies will ultimately contribute to medicinal plants' research and increased production of secondary metabolites, either through transgenic plants or through synthetic biology approaches. This review compiles studies on MYB transcription factors that are involved in the regulation of diverse functions in medicinal plants.

Heavy metal and metalloid toxicity in horticultural plants: Tolerance mechanism and remediation strategies

Heavy metal/metalloids (HMs) are among the primary soil pollutants that limit crop production worldwide. Plants grown in HM contaminated soils exhibit reduced growth and development, resulting in a decrease in crop production. The exposure to HMs induces plant oxidative stress due to the formation of free radicals, which alter plant morphophysiological and biochemical mechanisms at cellular and tissue levels. When exposed to HM toxicity, plants evolve sophisticated physiological and cellular defense strategies, such as sequestration and transportation of metals, to ensure their survival. Plants also have developed efficient strategies by activating signaling pathways, which induce the expression of HM transporters. Plants either avoid the uptake of HMs from the soil or activate the detoxifying mechanism to tolerate HM stress, which involves the production of antioxidants (enzymatic and non-enzymatic) for the scavenging of reactive oxygen species. The metal-binding proteins including phytochelatins and metallothioneins also participate in metal detoxification. Furthermore, phytohormones and their signaling pathways also help to regulate cellular activities to counteract HM stress. The excessive levels of HMs in the soil can contribute to plant morpho-physiological, biochemical, and molecular alterations, which have a detrimental effect on the quality and productivity of crops. To maintain the commercial value of fruits and vegetables, various measures should be considered to remove HMs from the metal-polluted soils. Bioremediation is a promising approach that involves the use of tolerant microorganisms and plants to manage HMs pollution. The understanding of HM toxicity, signaling pathways, and tolerance mechanisms will facilitate the development of new crop varieties that help in improving phytoremediation.