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AbstractThe demethylation status of pectin, a major plant cell wall polysaccharide, is regulated by pectin methylesterases (PMEs) and their endogenous inhibitors (PMEIs). While PME-mediated removal of methyl groups increases pectin susceptibility to enzymatic degradation and facilitates wall remodeling, this process is suppressed by PMEIs to strengthen the wall, preventing pathogen invasion. How biotrophic pathogens overcome this inhibitory defense remains unclear. Here, we demonstrate how N-glycosylation serves as a post-translational mechanism that pre-shapes a conserved smut effector, directing its adaptation toward a host-specific PMEI to facilitate colonization. We identify the Ustilago maydis N-glycosylated effector Nge1, which interacts with two host inhibitors, PMEI45 and PMEI46, to suppress their inhibitory function. This release of PME activity leads to highly demethylated pectin in the host cell wall that is prone to degradation, likely driving the cell wall loosening favored by pathogens. Crucially, we show that N-glycosylation of Nge1 is essential for its interaction with PMEI45, whereas the interaction with PMEI46 is glycosylation-independent. Engineering N-glycosylation sites into a naturally non-glycosylated Nge1 ortholog restored its ability to neutralize host PMEIs and functionally complement the U. maydis Δnge1 mutant. Our findings reveal that smut fungi utilize post-translational glycan modifications to fine-tune effector specificity, allowing them to overcome host-adapted PMEIs and manipulate plant cell wall dynamics in an ongoing plant-fungal interplay.Read more

AbstractDELLA proteins are negative regulators of gibberellin (GA) signaling. Under GA-deficient conditions, DELLA accumulates in the nucleus and interacts with numerous transcription factors (TFs) via the GRAS domain. Recent studies have shown that DELLA interacts with TFs via the LHR1 subdomain and histone H2A via the PFYRE subdomain, respectively. It is essential for DELLA-mediated global transcription reprogramming. DELLA exhibits strong transcriptional activity and acts as a co-activator of GAI-ASSOCIATED FACTOR1 (GAF1)/IDD2. The N-terminus of DELLA is necessary for strong transcriptional activity, but the regulatory activities and mechanisms of DELLA remain unclear. Therefore, we screened DELLA-interacting factors using the proximity biotinylation enzyme AirID and identified HISTONE ACETYLTRANSFERASE OF THE CBP FAMILY1 (HAC1). HAC1-mediated acetylation of histone H3 at the GAF1 target chromatin was necessary for transcriptional activation by the GAF1-DELLA complex. Additionally, the HAC1-mediated transcriptional activity of DELLA was involved in regulating plant growth. Moreover, ETHYLENE RESPONSE FACTOR2 (ERF2) was identified as a growth repressor gene regulated by the GAF1-DELLA-HAC1 complex. Here, we showed that DELLA proteins regulate plant growth via HAC1-mediated transcriptional regulation of ERF2.Read more

AbstractFaithful pollen wall formation requires tight control of both the amplitude and duration of tapetal transcriptional activity. However, how such dynamic restraint is achieved during anther development remains poorly understood. Here, we identify a phosphorylation-dependent regulatory module in which SBI-PP2A-C1/C5 constrains the functional activity window of the tapetal transcription factor bHLH089 to safeguard male fertility. PP2A-C1 and PP2A-C5 physically associate with bHLH089 and limit its transcriptional output by reducing bHLH089 phosphorylation and nuclear retention, thereby restricting its nuclear accumulation and effective activity. Genetic analyses reveal that precise PP2A-C1/C5 dosage is critical for pollen wall integrity, as both reduced PP2A-C function and PP2A-C1/C5 overexpression disrupt tapetal transcriptional homeostasis and compromise male fertility. Mechanistically, Ser28 and Ser58 function as conserved phosphorylation-dependent determinants of bHLH089 nuclear retention and are required for PP2A-C1/C5-sensitive regulation of bHLH089 activity. Together, these findings identify a phosphatase-mediated timing mechanism that integrates transcriptional feedback with post-translational control to constrain bHLH089-driven transcriptional amplification within a self-limiting tapetal activity window required for tapetal homeostasis, pollen wall formation, and male fertility.Read more

AbstractCold stress is a major environmental factor limiting the cultivation and productivity of grapevine (Vitis vinifera L.). While microRNAs (miRNAs) are well-established post-transcriptional regulators, the functional roles of microRNA-encoded peptides (miPEPs) in cold adaptation remain poorly understood. Through quantitative proteomics, we identified miPEP171b, encoded within the pri-miR171b transcript, as a key regulator of the grapevine cold stress response. Cold stress induces pri-miR171b expression, significantly upregulating both miPEP171b and pre-miR171b. As a small peptide, miPEP171b further promotes the accumulation of vvi-miR171b. Further studies demonstrate that miPEP171b and vvi-miR171b enhance cold tolerance by suppressing their target gene, VvSCL15, which acts as a negative regulator of the cold stress response. Under normal conditions, VvSCL15 recruits the histone deacetylase VvHDA19 to form a regulatory complex, which maintains low histone H3 acetylation levels and suppresses the expression of key cold-responsive genes, such as VvCOR27, VvCAM-1, and VvCML46. Upon cold exposure, the accumulation of miPEP171b and vvi-miR171b suppresses the expression of VvSCL15, dismantling this repressor complex and initiating extensive transcriptional reprogramming. Metabolomic profiling further confirms that miPEP171b orchestrates adaptive shifts in amino acid and sugar metabolism. Collectively, our findings define a novel miPEP171b-miR171b-SCL15/HDA19 module that integrates peptide signaling with chromatin remodeling to confer cold tolerance in grapevine. This study uncovers a previously unrecognized epigenetic switch for cold adaptation and provides a strategic target for enhancing environmental resilience in horticultural crops.Read more

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