The results suggest that BlOFP1 is associated with reduced SCW formation in these experimental systems, whereas the endogenous function of BlOFP1 in B. luminifera remains to be established.
Abstract
Timber quality is strongly influenced by the structure of the secondary cell wall (SCW). Ovate family proteins (OFPs) have been reported to regulate SCW formation in Arabidopsis. However, the functions of OFP proteins in woody plants remain unclear. In this study, an OFP gene, BlOFP1, was identified by co-expression analysis in Betula luminifera. BlOFP1 was co-expressed with multiple genes associated with lignin and cellulose biosynthesis. The subcellular localization showed that BlOFP1 was localized in the nucleus of tobacco leaf epidermal cells. Overexpression of BlOFP1 in Arabidopsis reduced cellulose, hemicellulose, and lignin contents and resulted in thinner SCW. In B. luminifera hairy roots, overexpression of BlOFP1 also led to thinner SCW, suggesting that elevated BlOFP1 expression is associated with reduced SCW formation in these experimental systems. Yeast two-hybrid, bimolecular fluorescence complementation and co-immunoprecipitation assays further showed that BlOFP1 physically interacted with BlKNOX9 and BlBLH9. Overall, our results suggest that BlOFP1 is associated with reduced SCW formation in these experimental systems, whereas the endogenous function of BlOFP1 in B. luminifera remains to be established. BlOFP1 may act together with BlKNOX9 and BlBLH9 in a proposed regulatory module.
Powdery mildew fungi induce localized endoreduplication, a variant of the cell cycle in which DNA is replicated but cells do not divide, in leaf mesophyll cells underlying the fungal feeding structure. Induced endoreduplication occurs concurrent with powdery mildew (PM) spore production and is associated with enhanced metabolic capacity and flux to lipids. The final ploidy of these cells is highly correlated with fungal spores produced and is the consequence of both basal (developmental) ploidy and PM-induced endoreduplication programs. Herein, we find the Arabidopsis lipid trafficking and regulatory protein ACYL-COA BINDING PROTEIN 4 (ACBP4) enhances PM spore production on Arabidopsis leaves. ACBP4 does not limit plant defense but instead supports basal mesophyll cell ploidy, with decreased final ploidy in cells underlying the fungal feeding structure in acbp4 mutants compared to wild-type (WT). Leaf epidermal cell size is decreased and stomatal density is increased in acbp4, consistent with a role for ACBP4 in developmentally programmed endoreduplication. Moreover, hypocotyl elongation in the dark, which is driven by programmed developmental endoreduplication, shows reduced hypocotyl length, cell length and ploidy in acbp4 versus WT. Together, our findings establish a novel means by which a plant ACBP promotes cell metabolism and development, with potential applications to agricultural productivity and quality.
Prickles are specialized hardening outgrowths characterized by the lignin deposition, the primary component of secondary cell walls (SCWs). While NAC transcription factors are known to function as crucial regulators of SCW formation through hierarchical transcriptional networks, their specific roles in prickle lignification and hardening in Rosa species have yet to be fully elucidated. In this study, we identified a NAC transcription factor in R. multiflora, RmPPN1, which exhibits preferential expression in developing and mature prickles. Ectopic expression of RmPPN1 significantly enhanced lignin accumulation in transgenic Arabidopsis. Through yeast two-hybrid screening of a prickle cDNA library, we isolated RmBZR1 as an interactor partner of RmPPN1. Expression analysis revealed that RmBZR1 displays the highest expression in initial prickles, a pattern that is complementary to the expression profile of RmPPN1. Exogenous application of brassinolide (BL) and its inhibitor brassinazole (BRZ) exerted opposing effects on lignin accumulation in developing prickles during early morphogenesis. Functional characterization of RmBZR1 demonstrated its negative regulation on lignin biosynthesis. Exogenous treatment with BRZ effectively rescued the phenotype of reduction in lignin content. Furthermore, RmBZR1 binds to PAL1 promoter and represses its transcription, while RmPPN1 protein physically interacts with RmBZR1 to alleviate its suppression of the PAL1 promoter. Together, these findings suggest a novel feedback regulatory module in which RmPPN1 and RmBZR1 coordinately control lignin biosynthesis during prickle development.
Yu Zhang, Junjie Wu, Yuzhen Li et al.· International Journal of Bio...· 0 citations
Xylem development involves a series of coordinated processes, including cell differentiation, expansion, secondary cell wall (SCW) deposition, and programmed cell death (PCD). Here, we characterize a subtilisin-like serine protease gene, SBT4.1, which exhibits specific expression in stem xylem. Loss of SBT4.1 function results in reduced xylem cell number, smaller cell size, thinner secondary walls, and delayed organelle degradation during PCD. In contrast, SBT4.1 overexpression accelerates cellular clearance and increases xylem cell number, size, and wall thickness, indicating its critical roles in differentiation, SCW synthesis, and PCD. Consistent with a positive regulatory function, pectinase activity and the expression of pectin-related genes are decreased in the mutant but increased in overexpressors. Accordingly, SBT4.1 promotes cell expansion, at least partly, by modulating pectinase activity, as evidenced by enhanced pectin methylesterase (PME) activity upon co-expression with specific PME genes in Nicotiana benthamiana. Molecular analyses revealed that SBT4.1 is a direct transcriptional target of the key SCW regulators SND1, VND6, and MYB46. Furthermore, the expression of SCW synthesis-related genes and PCD-associated protease genes is downregulated in the mutant and upregulated in overexpressing plants. Taken together, our findings demonstrate that SBT4.1, transcriptionally activated by SND1/VND6/MYB46, coordinates xylem cell differentiation, SCW deposition, and PCD, while also promoting cell expansion through modulation of pectin metabolism.
Chong Zhang, Yaoming Xu, Ziyu Ge et al.· Plant physiology and biochem...· 0 citations
The identified SlPAE genes were classified phylogenetically into three conserved subfamilies, with branch members sharing domain architectures, motifs, and genomic structure, providing a much-needed framework for future research into their specific biological roles in tomatoes.
Ruizhen Li, Lin Shen, Jianzhong Tie et al.· BMC Plant Biology· 0 citations
A WRKY-MYB cascade that mediates SCW formation in H. brasiliensis is revealed, extending the classical NAC-MYB regulatory framework and providing molecular targets for improving xylem properties and stress resilience in tropical perennial crops.
Jinjing Pan, Yanhong Xu, Junchao Zhao et al.· Plant, Cell and Environment· 0 citations
Chaperones are essential for Clp protease that governs protein quality control in chloroplast. However, it remains poorly understood whether and how individual ClpC proteins play distinct roles in plant growth and development. In this study, we isolated a new allele of clpc2, designated sot11, from genetic suppressor screening of the thf1 leaf variegation phenotype. DNA sequencing combined with protein structural modeling revealed that the sot11 mutation causes a substitution of Thr to Ile at position 868 located within a loop region of ClpC2, leading to partial loss-of-function of ClpC2. Genetic and phenotypic assays demonstrated that sot11 suppresses not only thf1-mediated but also var2/ftsh2-mediated leaf variegation. Notably, sot11 fails to restore high-light hypersensitivity and the reduced FtsH protease levels observed in thf1. In addition, CRISPR-Cas9-generated complete knockout mutants of clpc2 exhibit severe growth retardation, markedly shortened roots, and pronounced anthocyanin accumulation, compared to the wild type (WT) plants, revealing a dosage-dependent relationship between ClpC2 activity and plant fitness. Taken together, these findings suggest that ClpC2 plays an important role in both shoot and root growth, opening a new avenue for investigating the organ-specific molecular mechanisms underlying ClpC2 function.
Xiao-Mei Chen, Ting Guo, Danni Lin et al.· Biochemical and Biophysical...· 0 citations
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