Cliff habitats are characterized by limited and heterogeneous water availability, requiring plants to develop adaptive strategies to cope with drought stress. Opisthopappus longilobus, a cliff-endemic Asteraceae species restricted to the Taihang Mountains of northern China, has evolved under persistent water-limited conditions and represents a valuable model for investigating the molecular mechanisms underlying drought adaptation. However, the transcriptional regulatory networks involved in its drought response remain largely unexplored. In this study, we performed RNA sequencing of O. longilobus leaves under control and drought conditions to investigate drought-responsive regulatory networks. Six RNA-seq libraries were generated, and a total of 5260 differentially expressed genes (DEGs) were identified in response to drought stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that these DEGs were mainly associated with phytohormone signal transduction, stress-responsive regulation, defense responses, metabolic reprogramming, and transcriptional regulation. Notably, multiple transcription factor families, including MYB, ERF, and ABF, were enriched among drought-responsive genes, suggesting their involvement in drought adaptation. Furthermore, quantitative RT-PCR was used to validate the RNA-seq results. Among the drought-responsive transcription factors, an R2R3-MYB transcription factor, OlMYB35, was identified as a candidate regulator and was further demonstrated to play a positive role in drought response through transient transformation assays. Taken together, this study provides new insights into drought-responsive regulatory mechanisms in O. longilobus and identifies OlMYB35 as a promising candidate gene for further functional validation and potential application in stress-resilient chrysanthemum breeding.
Ruyue Jing, Yaru Zhang, Xiao-Jin Su et al.· Horticulturae· 0 citations
Flowering is a crucial process in the growth and development of plants, playing an essential role in their life cycles. Thus, research into the regulation of flowering time holds significant importance. While CmBBX7 has been identified as a flowering activator regulated by photoperiod, the molecular mechanisms underlying its regulation at the protein level remain unclear. In this study, we utilized yeast two-hybrid screening to identify two proteins that interact with CmBBX7: the phosphatase CmPP6 and the E3 ubiquitin ligase CmMIEL1. Ubiquitination assays confirmed that CmMIEL1 promotes the degradation of CmBBX7, thereby affecting its protein stability and influencing flowering. Genetic evidence indicated that both CmPP6 and CmMIEL1 delay flowering. By interacting with CmBBX7, they indirectly repress the expression of CmFTL1, which is a key flowering gene in chrysanthemum. Our findings provide preliminary evidence that ubiquitin modification affects the stability of the CmBBX7 protein and thereby regulates flowering in chrysanthemum.
Yuqing Zhu, Jinyu Jin, Yiwen Zhai et al.· Plant physiology and biochem...· 0 citations
Black spot disease (BSD), caused by Alternaria alternata, is a devastating threat to the chrysanthemum industry, yet its genetic basis remains largely elusive. The present study aimed to decipher the genetic architecture of chrysanthemum BSD resistance and to discover genetic loci and candidate genes using genome-wide association studies (GWAS) in a biparental F1 population (n = 164). Phenotypic evaluations of BSD resistance were conducted using both multi-stage detached-leaf assays and seedling-stage in vivo inoculations. The disease severity index (DSI) exhibited wide coefficient of variation (CV: 26.21%–54.84%) and high broad-sense heritability (0.71–0.95), with significant transgressive segregation observed in the F1 progeny. 375 865 high-quality SNPs-based GWAS identified 220 quantitative trait nucleotides (QTNs) and 36 QTN-by-environment interactions (QEIs), explaining up to 7.39% and 3.46% of the phenotypic variance, respectively. Among 26 stable QTNs, 17 favorable alleles displayed significant additive effects and a clear dosage-pyramiding effect (P < 0.001). By integrating functional annotation with transcriptome profiling, 34 candidate genes involved in immune defense were identified within the candidate intervals. Notably, three key candidate genes, CmABF1, CmSINAT3, and CmLTPG1, were validated as positive regulators of BSD resistance through transient overexpression and silencing assays. The research findings provide crucial genetic resources for the molecular improvement of resistance to BSD in chrysanthemums.
Ying Li, Xiao Chen, Xinjing Lai et al.· Horticulture Research· 0 citations
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