Genome-wide analysis of the CCT gene family in Chinese white pear (Pyrus bretschneideri Rehd.) and characterization of PbPRR2 in response to varying light signals

Positive regulation of BBX11 by NAC053 confers stomatal and apoplastic immunity against bacterial infection in Arabidopsis

Stomatal immunity and apoplastic immunity are critical for preventing microbial phytopathogenesis. However, the specific regulatory mechanisms of these resistances remain unclear. In this study, a BBX11 transcription factor (TF) was identified in Arabidopsis and was found to participate in stomatal and apoplast immunity. Phenotypic, biochemical, and genetic analyses revealed that NAC053 contributed to Arabidopsis resistance against Pseudomonas syringae pv tomato DC3000 (Pst DC3000) by positively regulating BBX11. BBX11 TF that was expressed constitutively in guard cells acts as a positive regulator of plant defense against Pst DC3000 through the suppression of coronatine (COR)-induced stomatal reopening, mitigating the virulence of COR and alleviating COR-triggered systemic susceptibility in the apoplast. BBX11 was found to be involved in PTI responses induced by flg22, such as stomatal closure, reactive oxygen species accumulation, MAPK activation, and callose deposition, thereby enhancing disease resistance. Yeast one-hybrid screening identified NAC053 as a potential TF that interacted with the promoter of BBX11. NAC053 also positively regulated resistance to Pst DC3000. These findings underscore the significance of transcriptional activation of BBX11 by NAC053 in stomatal and apoplastic immunity against Pst DC3000, enhancing understanding of plant regulatory mechanisms in response to bacterial pathogens.

A B-Box (BBX) Transcription Factor from Cucumber, CsCOL9 Positively Regulates Resistance of Host Plant to Bemisia tabaci

B-box (BBX) transcription factors play crucial roles in plant growth, development, and defense responses to biotic and abiotic stresses. In this study, we cloned a BBX transcription factor gene, CsCOL9I, from cucumber and analyzed its role in the plant's defense against the feeding of Bemisia tabaci. CsCOL9 is expressed throughout all developmental stages in cucumber, with the highest expression in the leaves. CsCOL9 is induced by B. tabaci feeding, salicylic acid (SA), methyl jasmonate (MeJA), and hydrogen peroxide (H2O2). Cucumber plants with CsCOL9 silence (TRV2-CsCOL9) and overexpression (1301-CsCOL9) were obtained and analyzed. After CsCOL9 silencing, survival rates and host selectivity for B. tabaci increased; however, the expression levels of genes encoding enzymes (CsSOD, CsRBOH, CsPOD), activities of superoxide dismutase (SOD) and peroxidase (POD), and content of H2O2 in plants were all reduced. CsCOL9 overexpression led to decreased survival rates and host selectivity for B. tabaci. Conversely, the expression levels of genes (CsSOD, CsRBOH and CsPOD), activities of SOD and POD, and content of H2O2 increased after CsCOL9 overexpression in plants. Collectively, our results demonstrate CsCOL9 positively regulates cucumber resistance to B. tabaci by activating reactive oxygen species bursts. This study lays a theoretical foundation for the application of CsCOL9 in cucumber resistance breeding and green pest control of B. tabaci.

Genome-Wide Identification and Expression Profiling Analysis of the CCT Gene Family in Solanum lycopersicum and Solanum melongena

CCT family genes play crucial roles in photoperiodic flowering and environmental stress response; however, there are limited reports in Solanum species with considerable edible and medicinal value. In this study, we conducted genome-wide characterization and expression profiling analysis of the CCT gene family in two Solanum species: tomato (Solanum lycopersicum L.) and eggplant (Solanum melongena L.). A total of 27 SlCCT and 29 SmCCT genes were identified in the tomato and eggplant genomes, respectively. Phylogenetic analysis showed that the CCT gene family could be divided into six subgroups (COL I, COL II, COL III, PRR, CMF I, and CMF II) in Oryza sativa and Arabidopsis thaliana. The similarity in the distribution of exon-intron structures and conserved motifs within the same subgroup indicated the conservation of SlCCT and SmCCT genes during evolution. Intraspecies collinearity analysis revealed that six pairs of SlCCT genes and seven pairs of SmCCT genes showed collinear relationships, suggesting that segmental duplication played a vital role in the expansion of the SlCCT and SmCCT family genes. Cis-acting element prediction indicated that SlCCT and SmCCT were likely to be involved in multiple responses stimulated by light, phytohormones, and abiotic stress. RT-qPCR analysis revealed that SmCCT15, SlCCT6/SlCCT14, and SlCCT23/SmCCT9 responded significantly to salt, drought, and cold stress, respectively. Our comprehensive analysis of the CCT gene family in tomato and eggplant provides a basis for further studies on its molecular role in regulating flowering and resistance to abiotic stress, and provides valuable candidate gene resources for tomato and eggplant molecular breeding.

Genome-Wide Identification and Characterization of CCT Gene Family from Microalgae to Legumes

The CCT (CO, COL and TOC1) gene family has been elucidated to be involved in the functional differentiation of the products in various plant species, but their specific mechanisms are poorly understood. In the present investigation, we conducted a genome-wide identification and phylogenetic analysis of CCT genes from microalgae to legumes. A total of 700 non-redundant members of the CCT gene family from 30 species were identified through a homology search. Phylogenetic clustering with Arabidopsis and domain conservation analysis categorized the CCT genes into three families. Multiple sequence alignment showed that the CCT domain contains important amino acid residues, and each CCT protein contains 24 conserved motifs, as demonstrated by the motif analysis. Whole-genome/segment duplication, as well as tandem duplication, are considered to be the driving forces in the evolutionary trajectory of plant species. This comprehensive investigation into the proliferation of the CCT gene family unveils the evolutionary dynamics whereby WGD/segment duplication is the predominant mechanism contributing to the expansion of the CCT genes. Meanwhile, the examination of the gene expression patterns revealed that the expression patterns of CCT genes vary in different tissues and at different developmental stages of plants, with high expression in leaves, which is consistent with the molecular regulation of flowering in photosynthesis by CCT. Based on the protein-protein interaction analysis of CCT genes in model plants, we propose that the CCT gene family synergistically regulates plant development and flowering with light-signaling factors (PHYs and PIFs) and MYB family transcription factors. Understanding the CCT gene family's molecular evolution enables targeted gene manipulation for enhanced plant traits, including optimized flowering and stress resistance.

Comparative physiological, metabolomic and transcriptomic analyses reveal the mechanisms of differences in pear fruit quality between distinct training systems

BACKGROUND

Canopy architecture is critical in determining the fruit-zone microclimate and, ultimately, in determining an orchard's success in terms of the quality and quantity of the fruit produced. However, few studies have addressed how the canopy environment leads to metabolomic and transcriptomic alterations in fruits. Designing strategies for improving the quality of pear nutritional components relies on uncovering the related regulatory mechanisms.

RESULTS

We performed an in-depth investigation of the impact of canopy architecture from physiological, metabolomic and transcriptomic perspectives by comparing pear fruits grown in a traditional freestanding system (SP) or a flat-type trellis system (DP). Physiological studies revealed relatively greater fruit sizes, soluble solid contents and titratable acidities in pear fruits from DP systems with open canopies. Nontargeted metabolite profiling was used to characterize fruits at the initial ripening stage. Significant differences in fruit metabolites, including carbohydrates, nucleic acids, alkaloids, glycerophospholipids, sterol lipids, and prenol lipids, were observed between the two groups. Transcriptomic analysis indicated that a series of organic substance catabolic processes (e.g., the glycerol-3-phosphate catabolic process, pectin catabolic process and glucan catabolic process) were overrepresented in fruits of the DP system. Moreover, integrative analysis of the metabolome and transcriptome at the pathway level showed that DP pear fruits may respond to the canopy microenvironment by upregulating phenylpropanoid biosynthesis pathway genes such as PpPOD. Transient assays revealed that the contents of malic acid and citric acid were lower in the pear flesh of PpPOD RNAi plants, which was associated with regulating the expression of organic acid metabolism-related genes.

CONCLUSIONS

Our results provide fundamental evidence that at the physiological and molecular levels, open-canopy architecture contributes to improving pear fruit quality and is correlated with increased levels of carbohydrates and lipid-like molecules. This study may lead to the development of rational culture practices for enhancing the nutritional traits of pear fruits.