Shoot apical meristem (SAM) and root apical meristem (RAM) homeostasis is tightly regulated by CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION-related (CLE) peptide signaling. However, the intracellular signaling components after CLV3 is perceived by the CLV1–CLV3-INSENSITIVE KINASE (CIK) receptor complex and CLE25/26/45 are sensed by the BARELY ANY MERISTEM (BAM)–CIK receptor complex are unknown. Here, we report that PBS1-LIKE34/35/36 (PBL34/35/36), a clade of receptor-like cytoplasmic kinases, are required for both CLV3-mediated signaling in the SAM and CLE25/26/45-mediated signaling in the RAM. Physiological assays showed that the SAM and RAM of pbl34 pbl35 pbl36 were resistant to CLV3 and CLE25/26/45 treatment, respectively. Genetic analyses indicated that pbl34 pbl35 pbl36 greatly enhanced the SAM defects of clv2 and rpk2 but not clv1, and did not show additive effects with bam3 and cik2 in the RAM. Further biochemical assays revealed that PBL34/35/36 interacted with CLV1, BAM1/3, and CIKs, and were phosphorylated by CLV1 and BAM1. All these results suggest that PBL34/35/36 act downstream of CLV1 and BAM1/3 to mediate the CLV3 and CLE25/26/45 signals in maintaining SAM and RAM homeostasis, respectively. Our findings shed light on how CLE signals are transmitted intracellularly after being perceived by cell surface receptor complexes.

Soil salinity is a major abiotic stress limiting crop production globally. Oat (Avena sativa) is an annual cereal with a strong salt tolerance, a high yield, and nutritional quality, although the mechanisms underlying its salt stress response remain largely unknown. We examined the physiological and transcriptomic responses of A. sativa seedlings to salt stress in tolerant cultivar Qingyongjiu 195 and sensitive cultivar 709. Under salt stress, Qingyongjiu 195 maintained a higher photosynthetic efficiency, antioxidant enzymes activity, and leaf K⁺ accumulation but a lower Na⁺ uptake than 709. RNA-seq revealed 6616 differentially expressed genes (DEGs), including 4265 up- and 2351 downregulated. These were enriched in pathways like plant–pathogen interaction, phenylpropanoid biosynthesis, and MAPK signaling. We specifically highlight DEGs involved in photosynthesis (chlG, CP47 psbB, COX2, LHCB) and antioxidants (trxA, GroES). Qingyongjiu 195 also appeared to enhance K⁺ uptake via KAT1 and AKT2 and sequester Na⁺ in vacuoles via NHX2. Additionally, HKT restricted Na⁺ while promoting K⁺ transport to shoots, maintaining K⁺/Na⁺. The expression levels of CAX, ACA, CML, CaM, and CDPK in Qingyongjiu 195 were higher than those in 709. Oats regulated Ca²⁺ concentration through CAX and ACA after salt stress, decoded Ca²⁺ signals through CML, and then transferred Ca²⁺ signals to downstream receptors through the Ca²⁺ sensors CaM and CDPK, thereby activating K⁺/Na⁺ transporters, such as SOS1 and NHX, etc. Our results shed light on plant salt stress response mechanisms and provide transcriptomic resources for molecular breeding in improving salt tolerance in oats.

Plant protein phosphatase 2C (PP2C) represents the largest and most functionally diverse group of protein phosphatases in plants, playing pivotal roles in regulating metabolic processes, hormone signaling, stress responses, and growth regulation. Despite its significance, a comprehensive genome-wide analysis of the PP2C gene family in oat (Avena sativa L.) has remained unexplored. Leveraging the recently published oat genome, we identified 194 AsaPP2C genes, which were unevenly distributed across all 21 chromosomes. A phylogenetic analysis of PP2C classified these genes into 13 distinct subfamilies (A-L), with conserved motif compositions and exon-intron structures within each subfamily, suggesting evolutionary functional specialization. Notably, a promoter analysis revealed an abundance of stress-responsive cis-regulatory elements (e.g., MYB, MYC, ARE, and MBS), implicating AsaPP2Cs in hormones and biotic stress adaptation. To elucidate their stress-responsive roles, we analyzed transcriptomic data and identified seven differentially expressed AsaPP2C (Asa_chr6Dg00217, Asa_chr6Ag01950, Asa_chr3Ag01998, Asa_chr5Ag00079, Asa_chr4Cg03270, Asa_chr6Cg02197, and Asa_chr7Dg02992) genes, which were validated via qRT-PCR. Intriguingly, these genes exhibited dynamic expression patterns under varying stress conditions, with their transcriptional responses being both time-dependent and stress-dependent, highlighting their regulatory roles in oat stress adaptation. Collectively, this study provides the first comprehensive genomic and functional characterization of the PP2C family in oat, offering valuable insights into their evolutionary diversification and functional specialization.

Chemical mutagenesis coupled with molecular marker analysis is an efficient strategy for accelerating crop improvement and creating crop genetic diversity, yet optimized protocols and comprehensive evaluations chemical mutagenesis-assisted forage oats traits improvement and breeding understudied. This study aimed to assess sodium azide (SA)-induced mutagenesis in two oat varieties (Everleaf and 709) by characterizing phenotypic and molecular variations, identifying tissue-specific mutation patterns, and establishing efficient treatment parameters for breeding. SA treatment at > 10 mmol·L⁻1 caused severe germination inhibition (lethality > 60%) but maximized phenotypic variation (CV up to 90.80% for panicle traits). By phenotypic screening, out of 767 (M2-M3) mutants, a total of six categories of mutant phenotypes were identified: leaf traits were most frequently altered (1.02%), followed by seeds (0.39%). M2 mutation frequencies reached 17.9–23.73%. SSR markers revealed high polymorphism (60–100% polymorphic sites, PIC 0.27–0.80), amplifying 3–9 alleles/locus. Multivariate analyses (PCA, UPGMA, and STRUCTURE) grouped 293 mutants into four genetically distinct clusters, confirming genome-wide diversity. SA induces extensive and diverse heritable phenotypic and molecular variations in oats, with mutation spectra showing tissue-specific trends. The mutant libraries and polymorphic SSR markers developed provide a valuable resource for oat breeding and functional genomics. This work establishes a protocol for SA mutagenesis in oats and delivers mutant germplasm with broad applicability in trait improvement and genetic research.

In light of the current global challenges, such as climate change, the overexploitation of natural resources, and increasing food demand, drought-tolerant forage crops present substantial potential for development in dryland regions. However, there is a notable gap in research that integrates yield improvement, nutritional quality enhancement, and resistance to pests and diseases in the production of forage crops in semi-arid areas. Therefore, selecting oat forage varieties that exhibit high yield, superior quality, and enhanced pest resistance can substantially advance the forage industry and animal husbandry in semi-arid regions. In this study, ten oat varieties, including both domestic and international cultivars, were cultivated in a semi-arid region (Weiqi town, Gansu Province) during the 2023–2024 growing season. A comprehensive analysis was performed to assess the yield, quality, and pest resistance of these varieties. All ten oat varieties successfully completed their growth cycles. Among them, Everleaf 126 exhibited a shorter plant height compared to the other varieties, measuring 103.32 cm and 115.14 cm over two years. However, its superior leaf area and tiller number led to the highest hay yields (11,819.33 kg/ha and 13,550.67 kg/ha) and seed yields (4913.20 kg/ha and 5242.33 kg/ha). Additionally, Everleaf 126 demonstrated significantly higher leaf–stem ratios (0.35 and 0.41), crude protein content (8.52% and 9.13%), and crude fat content (2.19% and 2.69%) relative to other oat varieties (p < 0.05). Furthermore, it showed the best resistance to powdery mildew (MR), red leaf disease (HR), leaf spot disease (MR), and aphids (R). The plant height of Kona was the lowest, measuring 81.22 cm and 87.16 cm, respectively, with the fewest number of tillers and the smallest leaf area. Baler II exhibited the lowest hay yield at 8770.10 kg/ha and 7898.33 kg/ha, as well as the lowest seed yield at 3409.33 kg/ha and 3323.90 kg/ha. Kona also had the lowest leaf–stem ratio (0.19 and 10.13) and crude protein content (5.74% and 6.58%), while exhibiting the highest neutral detergent fiber (NDF) and acid detergent fiber (ADF) values. Furthermore, Kona showed the poorest resistance to powdery mildew (MS) and leaf spot (MS). Finally, based on the comprehensive evaluation analysis of the membership function, in the semi-arid region, Everleaf 126 achieved the highest overall performance based upon a comprehensive evaluation, followed by Molasses and Longyan No.3. In comparison, Kona received the poorest performance.

The SWEET (Sugars Will Eventually be Exported Transporter) family, a class of sugar transporters identified in recent years, plays important roles in plant growth and development. Increasing evidence suggests that SWEET genes are also involved in plant responses to abiotic stresses, including salt stress. However, the genome-wide composition and salt-responsive functions of SWEET genes in Elymus nutans Griseb. have not been systematically characterized to date. This study presents the first genome-wide identification of the SWEET gene family in E. nutans and functional characterization of EnSWEET15 in salt stress response, providing candidate genes and a theoretical basis for improving salt tolerance in this species. A total of 12 EnSWEET genes were identified from the E. nutans genome and were unevenly distributed across eight chromosomes. Phylogenetic analysis classified them into four subfamilies, and promoter analysis revealed abundant cis-elements related to hormone signaling and stress responses, suggesting roles in abiotic stress adaptation. Expression analysis showed that EnSWEET15 was significantly upregulated in both roots and leaves under salt stress. The full-length EnSWEET15 coding sequence (930 bp ORF) was cloned and functionally characterized. Heterologous overexpression in Arabidopsis thaliana indicated that EnSWEET15 enhances salt tolerance. Transgenic lines showed reduced reactive oxygen species (ROS) accumulation and increased activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), compared with wild-type plants under salt stress. Overall, this study identifies EnSWEET15 as a positive regulator of salt tolerance via modulating ROS homeostasis, providing novel insights into SWEET-mediated salt stress response in perennial forages and valuable genetic resources for salt-tolerant breeding of E. nutans.