AtMYB2 transcription factor can interact with the CMO promoter and regulate its downstream gene expression

Overexpression of AtMYB2 Promotes Tolerance to Salt Stress and Accumulations of Tanshinones and Phenolic Acid in Salvia miltiorrhiza

Salvia miltiorrhiza is a prized traditional Chinese medicinal plant species. Its red storage roots are primarily used for the treatment of cardiovascular and cerebrovascular diseases. In this study, a transcription factor gene AtMYB2 was cloned and introduced into Salvia miltiorrhiza for ectopic expression. Overexpression of AtMYB2 enhanced salt stress resistance in S. miltiorrhiza, leading to a more resilient phenotype in transgenic plants exposed to high-salinity conditions. Physiological experiments have revealed that overexpression of AtMYB2 can decrease the accumulation of reactive oxygen species (ROS) during salt stress, boost the activity of antioxidant enzymes, and mitigate oxidative damage to cell membranes. In addition, overexpression of AtMYB2 promotes the synthesis of tanshinones and phenolic acids by upregulating the expression of biosynthetic pathway genes, resulting in increased levels of these secondary metabolites. In summary, our findings demonstrate that AtMYB2 not only enhances plant tolerance to salt stress, but also increases the accumulation of secondary metabolites in S. miltiorrhiza. Our study lays a solid foundation for uncovering the molecular mechanisms governed by AtMYB2 and holds significant implications for the molecular breeding of high-quality S. miltiorrhiza varieties.

Gene Expression Patterns in Roots of Camelina sativa With Enhanced Salinity Tolerance Arising From Inoculation of Soil With Plant Growth Promoting Bacteria Producing 1-Aminocyclopropane-1-Carboxylate Deaminase or Expression the Corresponding acdS Gene

Camelina sativa treated with plant growth-promoting bacteria (PGPB) producing 1-aminocyclopropane-1-carboxylate deaminase (acdS) or transgenic lines expressing acdS exhibit increased salinity tolerance. AcdS reduces the level of stress ethylene to below the point where it is inhibitory to plant growth. The study determined that several mechanisms appear to be responsible for the increased salinity tolerance and that the effect of acdS on gene expression patterns in C. sativa roots during salt stress is a function of how it is delivered. Growth in soil treated with the PGPB (Pseudomonas migulae 8R6) mostly affected ethylene- and abscisic acid-dependent signaling in a positive way, while expression of acdS in transgenic lines under the control of the broadly active CaMV 35S promoter or the root-specific rolD promoter affected auxin, jasmonic acid and brassinosteroid signaling and/biosynthesis. The expression of genes involved in minor carbohydrate metabolism were also up-regulated, mainly in roots of lines expressing acdS. Expression of acdS also affected the expression of genes involved in modulating the level of reactive oxygen species (ROS) to prevent cellular damage, while permitting ROS-dependent signal transduction. Though the root is not a photosynthetic tissue, acdS had a positive effect on the expression of genes involved in photosynthesis.

Characterization of wheat MYB genes responsive to high temperatures

BACKGROUND

Heat stress is one of the most crucial environmental factors, which reduces crop yield worldwide. In plants, the MYB family is one of the largest families of transcription factors (TFs). Although some wheat stress-related MYB TFs have been characterized, their involvement in response to high-temperature stress has not been properly studied.

RESULTS

Six novel heat-induced MYB genes were identified by comparison with previously established de novo transcriptome sequencing data obtained from wheat plants subjected to heat treatment; genomic and complete coding sequences of these genes were isolated. All six TaMYBs were localized in the nucleus of wheat protoplasts. Transactivation assays in yeast revealed that all six proteins acted as transcriptional activators, and the activation domains were attributed to the C-termini of the six wheat MYB proteins. Phylogenetic analysis of the six TaMYBs and R2R3-MYBs from Arabidopsis revealed that all six proteins were in clades that contained stress-related MYB TFs. The expression profiles of TaMYB genes were different in wheat tissues and in response to various abiotic stresses and exogenous abscisic acid treatment. In transgenic Arabidopsis plants carrying TaMYB80 driven by the CaMV 35S promoter, tolerance to heat and drought stresses increased, which could be attributed to the increased levels of cellular abscisic acid.

CONCLUSIONS

We identified six heat-induced MYB genes in wheat. We performed comprehensive analyses of the cloned MYB genes and their gene products, including gene structures, subcellular localization, transcriptional activation, phylogenetic relationships, and expression patterns in different wheat tissues and under various abiotic stresses. In particular, we showed that TaMYB80 conferred heat and drought tolerance in transgenic Arabidopsis. These results contribute to our understanding of the functions of heat-induced MYB genes and provide the basis for selecting the best candidates for in-depth functional studies of heat-responsive MYB genes in wheat.

Functional and Structural Characterization of a Receptor-Like Kinase Involved in Germination and Cell Expansion in Arabidopsis

Leucine-rich repeat receptor-like kinases (LRR-RLKs) are widespread in different plant species and play important roles in growth and development. Germination inhibition is vital for the completion of seed maturation and cell expansion is a fundamental cellular process driving plant growth. Here, we report genetic and structural characterizations of a functionally uncharacterized LRR-RLK, named GRACE (Germination Repression and Cell Expansion receptor-like kinase). Overexpression of GRACE in Arabidopsis exhibited delayed germination, enlarged cotyledons, rosette leaves and stubbier petioles. Conversely, these phenotypes were reversed in the T-DNA insertion knock-down mutant grace-1 plants. A crystal structure of the extracellular domain of GRACE (GRACE-LRR) determined at the resolution of 3.0 Å revealed that GRACE-LRR assumed a right-handed super-helical structure with an island domain (ID). Structural comparison showed that structure of the ID in GRACE-LRR is strikingly different from those observed in other LRR-RLKs. This structural observation implies that GRACE might perceive a new ligand for signaling. Collectively, our data support roles of GRACE in repressing seed germination and promoting cell expansion of Arabidopsis, presumably by perception of unknown ligand(s).