Characterization of pectin methylesterase gene family and its possible role in juice sac granulation in navel orange (Citrus sinensis Osbeck)

MYB transcription factor MdMYB44 positively regulates fruit crispness by directly activating the expression of pectin methylesterase MdMPE3 in apple

Crispness, a key attribute of fruit texture quality, is a critical determinant of apple commercial value. Pectin, a major component of the cell wall, plays a vital role in maintaining cell structure, turgor pressure, and mechanical support, with pectin methylesterase (PMEs, EC 3.1.1.11) mediating pectin modification during cell wall remodeling. In this study, we identified two genes, MdMYB44 and MdMPE3 (pectin methylesterase 3), that regulate apple fruit crispness. Through Y1H, EMSA, ChIP-qPCR, and transient expression assays, we demonstrated that the MYB transcription factor MdMYB44 directly enhances the expression of MdMPE3 by binding to its promoter. These results indicate that MdMYB44 acts as a positive regulator of fruit crispness by activating MdMPE3 transcription. Our findings provide new insights into the molecular mechanisms by which MYB transcription factors and pectin methylesterase influence apple fruit texture, enriching our understanding of the regulation of fruit crispness.

Coexpression Regulation of New and Ancient Genes in the Dynamic Transcriptome Landscape of Stem and Rhizome Development in "Bainianzhe"-An Ancient Chinese Sugarcane Variety Ratooned for Nearly 300 Years

The sucrose yield in sugarcane largely depends on stem morphology, including length, diameter and sugar content, making sugarcane stem a key trait in breeding. The "Bainianzhe" variety from Songxi County, Fujian Province, possesses both aerial stems and rhizomes, providing a unique model for studying stem development. We performed a spatiotemporal transcriptomic analysis of the base, middle and apical sections of both aerial stems and rhizomes. The analysis categorized transcriptomes by developmental stage-base, middle and apical-rather than environmental differences. Apical segments were enriched with genes related to cell proliferation, while base segments were linked to senescence and fibrosis. Gene regulatory networks revealed key TFs involved in stem development. Orphan genes may be involved in rhizome development through coexpression networks. Plant hormones, especially genes involved in ABA and GAs synthesis, were highly expressed in rhizomes. Thiamine-related genes were also more prevalent in rhizomes. Furthermore, the apical segments of rhizomes enriched in photosynthesis-related genes suggest adaptations to light exposure. Low average temperatures in Songxi have led to unique cold acclimation in Bainianzhe, with rhizomes showing higher expression of genes linked to unsaturated fatty acid synthesis and cold-responsive calcium signalling. This indicates that rhizomes may have enhanced cold tolerance, aiding in the plant's overwintering success.

GhPME36 aggravates susceptibility to Liriomyza sativae by affecting cell wall biosynthesis in cotton leaves

BACKGROUND

Cotton is an important economic crop and a host of Liriomyza sativae. Pectin methylesterase (PME)-mediated pectin metabolism plays an indispensable role in multiple biological processes in planta. However, the pleiotropic functions of PME often lead to unpredictable effects on crop resistance to pests. Additionally, whether and how PME affects susceptibility to Liriomyza sativae remain unclear.

RESULTS

Here, we isolated GhPME36, which is located in the cell wall, from upland cotton (Gossypium hirsutum L.). Interestingly, the overexpression of GhPME36 in cotton caused severe susceptibility to Liriomyza sativae but increased leaf biomass in Arabidopsis. Cytological observations revealed that the cell wall was thinner with more demethylesterified pectins in GhPME36-OE cotton leaves than in WT leaves, whereas the soluble sugar content of GhPME36-OE cotton leaf cell walls was accordingly higher; both factors attracted Liriomyza sativae to feed on GhPME36-OE cotton leaves. Metabolomic analysis demonstrated that glucose was significantly differentially accumulated. Transcriptomic analysis further revealed DEGs enriched in glucose metabolic pathways when GhPME36 was overexpressed, suggesting that GhPME36 aggravates susceptibility to Liriomyza sativae by affecting both the structure and components of cell wall biosynthesis. Moreover, GhPME36 interacts with another pectin-modifying enzyme, GhC/VIF1, to maintain the dynamic stability of pectin methyl esterification.

CONCLUSIONS

Taken together, our results reveal the cytological and molecular mechanisms by which GhPME36 aggravates susceptibility to Liriomyza sativae. This study broadens the knowledge of PME function and provides new insights into plant resistance to pests and the safety of genetically modified plants.

Genome-wide identification of walnut (Juglans regia) PME gene family members and expression analysis during infection with Cryptosphaeria pullmanensis pathogens

Walnuts exhibit a higher resistance to diseases, though they are not completely immune. This study focuses on the Pectin methylesterase (PME) gene family to investigate whether it is involved in disease resistance in walnuts. These 21 genes are distributed across 12 chromosomes, with four pairs demonstrating homology. Variations in conserved motifs and gene structures suggest diverse functions within the gene family. Phylogenetic and collinear gene pairs of the PME family indicate that the gene family has evolved in a relatively stable way. The cis-acting elements and gene ontology enrichment of these genes, underscores their potential role in bolstering walnuts' defense mechanisms. Transcriptomic analyses were conducted under conditions of Cryptosphaeria pullmanensis infestation and verified by RT-qPCR. The results showed that certain JrPME family genes were activated in response, leading to the hypothesis that some members may confer resistance to the disease.

Upgrading pectin methylation for consistently enhanced biomass enzymatic saccharification and cadmium phytoremediation in rice Ospmes site-mutants

Crop straws provide enormous biomass residues applicable for biofuel production and trace metal phytoremediation. However, as lignocellulose recalcitrance determines a costly process with potential secondary waste liberation, genetic modification of plant cell walls is deemed as a promising solution. Although pectin methylation plays an important role for plant cell wall construction and integrity, little is known about its regulation roles on lignocellulose hydrolysis and trace metal elimination. In this study, we initially performed a typical CRISPR/Cas9 gene-editing for site mutations of OsPME31, OsPME34 and OsPME79 in rice, and then determined significantly upgraded pectin methylation degrees in the young seedlings of three distinct site-mutants compared to their wild type. We then examined distinctively improved lignocellulose recalcitrance in three mutants including reduced cellulose levels, crystallinity and polymerization or raised hemicellulose deposition and cellulose accessibility, which led to specifically enlarged biomass porosity either for consistently enhanced biomass enzymatic saccharification under mild alkali pretreatments or for cadmium (Cd) accumulation up to 2.4-fold. Therefore, this study proposed a novel model to elucidate how pectin methylation could play a unique enhancement role for both lignocellulose enzymatic hydrolysis and Cd phytoremediation, providing insights into precise pectin modification for effective biomass utilization and efficient trace metal exclusion.