Ubiquitination plays important roles in modulating the abiotic stress tolerance of plants. Drought seriously restricts agricultural production, but how ubiquitination participates in regulating drought tolerance remains largely unknown. Here, we identified a drought-inducible gene, MYB30-INTERACTING E3 LIGASE 1 (GhMIEL1), which encodes a RING E3 ubiquitin ligase in cotton (Gossypium hirsutum). GhMIEL1 was strongly induced by polyethylene glycol (PEG-6000) and the phytohormone abscisic acid (ABA). Overexpression and knockdown of GhMIEL1 in cotton substantially enhanced and reduced drought tolerance, respectively. GhMIEL1 interacted with the MYB transcription factor GhMYB66 and could ubiquitinate and degrade it in vitro. GhMYB66 directly bound to the LONELY GUY 5 (GhLOG5) promoter, a gene encoding cytokinin riboside 5'-monophosphate phosphoribohydrolase, to repress its transcription. Overexpression of GhMIEL1 and silencing of GhMYB66 altered the homeostasis of cytokinin of plant roots, increased total root length and number of root tips, and enhanced plant drought tolerance. Conversely, silencing GhLOG5 decreased total root length and number of root tips and reduced plant drought tolerance. Our studies reveal that the GhMIEL1-GhMYB66-GhLOG5 module positively regulates drought tolerance in cotton, which deepens our understanding of plant ubiquitination-mediated drought tolerance and provides insights for improving drought tolerance.

Verticillium wilt, caused by Verticillium dahliae, is a soil-borne vascular disease that harms many plants, including cotton. The mitogen-activated protein kinase cascade is a highly conserved signal transduction pathway that transmits various extracellular stimuli to downstream targets during plant defense responses. Although there have been many studies on the key role of the mitogen-activated protein kinase cascade in plant disease resistance, mitogen-activated protein kinase signal transduction in cotton remains to be elucidated. Here, we found that GhMKK5 interacted with GhMPK13 and directly phosphorylated GhMPK13. Silencing the homolog GbMKK5 or GbMPK13 in Gossypium barbadense acc. Hai7124 significantly compromised resistance to V. dahliae, accompanied by reduced mitogen-activated protein kinase phosphorylation levels. Conversely, overexpression of GhMKK5 in Arabidopsis enhanced disease resistance and increased phosphorylation of AtMPK3/6. GhMPK13 can phosphorylate BRI1-EMS-SUPPRESSOR 1 (GhBES1), a core transcription factor in the brassinosteroid signaling pathway, which plays a negative regulatory role in resistance to V. dahliae by regulating the expression of pectate lyase 75 (GhPEL75). The phosphorylation of GhBES1 diminishes its binding ability to the promoter of GhPEL75, leading to reduced pectate lyase activity and enhanced disease resistance in cotton. In addition, another interacting protein of GhMPK13, GhSRC1, could improve the stability of GhMPK13, and silencing its expression decreased resistance to V. dahliae. Taken together, our results propose a mitogen-activated protein kinase pathway of GhMKK5-GhMPK13-GhBES1-GhPEL75 in regulating resistance to verticillium wilt in cotton, providing insights into the molecular mechanisms underlying plant cell wall adaptive alteration in the defense response.

Anthocyanins are important flavonoid compounds with significant antioxidant activity and ornamental value in rice. In this study, using upland rice landrace 17SM-19 as the material, the anthocyanin content in leaves was determined at the one-(S1) and two-leaf stages (S2). The anthocyanin content at S1 (43.37 U/g) was significantly higher than that at S2 (16.54 U/g). With S1 considered the control, a total of 9865 differentially expressed genes (DEGs) were identified in the S2, among which 4702 were upregulated and 5163 were downregulated. Functional enrichment analyses revealed that these DEGs were significantly enriched in terms and pathways such as photosynthesis and ribosome. Screening of these DEGs identified 10 structural genes and four regulatory genes associated with anthocyanin biosynthesis. Quantitative real-time PCR verified the reliability of the transcriptome data. These results provide valuable clues for revealing the molecular mechanism underlying anthocyanin biosynthesis in rice leaves.

Serine carboxypeptidase-like (SCPL) proteins play important roles in plant secondary metabolism, growth, and stress responses. Several SCPL members have been reported to participate in the biosynthesis of antimicrobial compounds associated with plant immunity. However, systematic characterization of the SCPL gene family in rice and its potential involvement in sheath blight (ShB) responses remains largely unclear. In this study, 45 SCPL genes were identified using the IRGSP-1.0 reference assembly and Ensembl Plants release 54 annotation and designated as OsSCPL1–OsSCPL45. Phylogenetic analysis of SCPL proteins from rice, Arabidopsis, soybean, and maize classified these proteins into three groups. Gene structures, conserved motifs, chromosomal distribution, and promoter cis-elements were subsequently analyzed. Chromosomal mapping and collinearity analysis revealed that both tandem and segmental duplications contributed to the expansion of the OsSCPL gene family. Promoter analysis identified numerous cis-elements associated with stress and hormone signaling. Mock-controlled RT-qPCR results of OsSCPL genes in resistant rice genotype YSBR1 and susceptible rice genotype Lemont (LE) showed that 14 OsSCPL genes were significantly up- or downregulated following Rhizoctonia solani inoculation in at least one genotype. The segmentally duplicated gene pair OsSCPL4 was significantly upregulated in both genotypes, whereas OsSCPL25 was significantly upregulated in YSBR1 but did not reach significance in LE. This study provides an updated genomic framework for the SCPL gene family in rice and suggests potential roles for OsSCPL4 and OsSCPL25 in rice responses to R. solani, laying a foundation for further functional studies.