Genome-Wide Characterization and Expression Profiling of the GRAS Gene Family in Salt and Alkali Stresses in Miscanthus sinensis

Small GTPase PvARFR2 interacts with cytosolic ABA receptor kinase 3 to enhance alkali tolerance in switchgrass

Soil alkalization has become a serious problem that limits plant growth through osmotic stress, ionic imbalance, and oxidative stress. Understanding how plants resist alkali stress has practical implications for alkaline-land utilization. In this study, we identified a small GTPase, PvARFR2 (ADP ribosylation factors related 2), that positively regulates alkali tolerance in switchgrass (Panicum virgatum) and uncovered its potential mode of action. Overexpressing PvARFR2 in switchgrass and Arabidopsis (Arabidopsis thaliana) conferred transformant tolerance to alkali stress, demonstrated by alleviated leaf wilting, less oxidative injury, and a lower Na+/K+ ratio under alkali conditions. Conversely, switchgrass PvARFR2-RNAi and its homolog mutant atgb1 in Arabidopsis displayed alkali sensitives. Transcriptome sequencing analysis showed that cytosolic abscisic acid (ABA) receptor kinase PvCARK3 transcript levels were higher in PvARFR2 overexpression lines compared to the controls and were strongly induced by alkali treatment in shoots and roots. Phenotyping analysis revealed that PvCARK3-OE × atgb1 lines were sensitive to alkali similar to the Arabidopsis atgb1 mutant, indicating that PvARFR2/AtGB1 functions in the same pathway as PvCARK3 under alkaline stress conditions. Application of ABA on PvARFR2-OE and PvCARK3-OE switchgrass transformants resulted in ABA sensitivity. Moreover, we determined that PvARFR2 physically interacts with PvCARK3 in vitro and in vivo. Our results indicate that a small GTPase, PvARFR2, positively responds to alkali stress by interacting with the cytosolic ABA receptor kinase PvCARK3, connecting the alkaline stress response to ABA signaling.

Genome-Wide Identification of GRAS Transcription Factors and Their Functional Analysis in Salt Stress Response in Sugar Beet

GAI-RGA-and-SCR (GRAS) transcription factors can regulate many biological processes such as plant growth and development and stress defense, but there are few related studies in sugar beet. Salt stress can seriously affect the yield and quality of sugar beet (Beta vulgaris). Therefore, this study used bioinformatics methods to identify GRAS transcription factors in sugar beet and analyzed their structural characteristics, evolutionary relationships, regulatory networks and salt stress response patterns. A total of 28 BvGRAS genes were identified in the whole genome of sugar beet, and the sequence composition was relatively conservative. According to the topology of the phylogenetic tree, BvGRAS can be divided into nine subfamilies: LISCL, SHR, PAT1, SCR, SCL3, LAS, SCL4/7, HAM and DELLA. Synteny analysis showed that there were two pairs of fragment replication genes in the BvGRAS gene, indicating that gene replication was not the main source of BvGRAS family members. Regulatory network analysis showed that BvGRAS could participate in the regulation of protein interaction, material transport, redox balance, ion homeostasis, osmotic substance accumulation and plant morphological structure to affect the tolerance of sugar beet to salt stress. Under salt stress, BvGRAS and its target genes showed an up-regulated expression trend. Among them, BvGRAS-15, BvGRAS-19, BvGRAS-20, BvGRAS-21, LOC104892636 and LOC104893770 may be the key genes for sugar beet's salt stress response. In this study, the structural characteristics and biological functions of BvGRAS transcription factors were analyzed, which provided data for the further study of the molecular mechanisms of salt stress and molecular breeding of sugar beet.

PvARL1 Increases Biomass Yield and Enhances Alkaline Tolerance in Switchgrass (Panicum virgatum L.)

Switchgrass is an important bioenergy crop valued for its biomass yield and abiotic tolerance. Alkali stress is a major abiotic stress that significantly impedes plant growth and yield due to high salinity and pH; however, the response mechanism of switchgrass to alkali stress remains limited. Here, we characterized PvARL1, an ARF-like gene, which was up-regulated in both the shoot and root tissues under alkali stress conditions. Overexpression of PvARL1 not only improved alkali tolerance but also promoted biomass yield with more tiller and higher plant height in switchgrass. Moreover, PvARL1 overexpression lines displayed higher capacities in the maintenance of water content and photosynthetic stability compared with the controls under alkali treatments. A significant reduction in the ratio of electrolyte leakage, MDA content, and reactive oxygen species (ROS) showed that PvARL1 plays a positive role in protecting cell membrane integrity. In addition, PvARL1 also negatively affected the K+ efflux or uptake in roots to alleviate ion toxicity under alkali treatments. Overall, our results suggest that PvARL1 functions as a positive regulator in plant growth as well as in the plant response to alkali stress, which could be used to improve switchgrass biomass yield and alkali tolerance genetically.

The Association between BZIP Transcription Factors and Flower Development in Litsea cubeba

The basic leucine zipper (bZIP) family is one of the largest families of transcription factors among eukaryotic organisms. Members of the bZIP family play various roles in regulating the intricate process of flower development in plants. Litsea cubeba (Lour.) (family: Lauraceae) is an aromatic, dioecious plant used in China for a wide range of applications. However, no study to date has undertaken a comprehensive analysis of the bZIP gene family in L. cubeba. In this work, we identified 68 members of the bZIP gene family in L. cubeba and classified them into 12 subfamilies based on previous studies on Arabidopsis thaliana. Transcriptome data analysis revealed that multiple LcbZIP genes exhibit significantly high expression levels in the flowers of L. cubeba, while some also demonstrate distinct temporal specificity during L. cubeba flower development. In particular, some LcbZIP genes displayed specific and high expression levels during the stamen and pistil degradation process. Using differential gene expression analysis, weighted gene co-expression network analysis, and Gene Ontology enrichment analysis, we identified six candidate LcbZIP genes that potentially regulate stamen or pistil degradation during flower development. In summary, our findings provide a framework for future functional analysis of the LcbZIP gene family in L. cubeba and offer novel insights for investigating the mechanism underlying pistil and stamen degeneration in this plant.