Plant and Cell Physiology最新文献

Chloroplasts in seed plants differentiate from proplastids or, occasionally, from other types of plastids. The development of the thylakoid membrane (TM) is a key process in chloroplast biogenesis, enabling plants to perform photosynthesis. The TM is a lipid bilayer membrane system densely packed with photosynthetic protein-cofactor complexes, and its formation requires the coordinated synthesis of membrane lipids, photosynthetic proteins, and cofactors particularly chlorophyll. During chloroplast biogenesis, membrane lipids are synthesized in the envelope membranes and transferred to the TM through yet unknown mechanisms. Chlorophyll biosynthesis and the synthesis of plastid-encoded proteins also occur in association with membranes, although their precise suborganellar sites, especially during early chloroplast development, remain unclear. In this review, we discuss the roles of the chloroplast envelope and internal membranes as potential origins of the TM during chloroplast development and then summarize current knowledge on the biosynthetic pathways of plastid membrane lipids, chlorophyll, and photosynthetic proteins. We further highlight recent findings on how plastid lipid biosynthesis contributes to the synthesis of chlorophyll and plastid-encoded proteins, as well as to the expression of photosynthesis-associated nuclear-encoded genes via plastid-to-nucleus retrograde signaling. Finally, we propose that plastid lipid biosynthesis triggers chloroplast biogenesis by initiating and coordinating membrane-associated processes required for TM formation.

Serine/arginine-rich (SR) proteins are essential splicing factors in animals, where their mutations often cause widespread splicing defects and carcinogenesis. The plant SR subfamily proteins are homologous to the well-studied human serine/arginine-rich splicing factor 1 (SRSF1), but their roles remain unclear. Here, we characterize the Arabidopsis SR subfamily genes: SR30, SR34, SR34a and SR34b. We show that GFP-tagged SR30, SR34 and SR34a co-localized with the spliceosomal protein U1-70K in speckled nuclear structures. To explore their physiological roles, we constructed a series of multiple mutants. Interestingly, the quadruple mutant displayed delayed flowering under long-day conditions but accelerated flowering under short-day conditions. Under long days, SR30, SR34 and SR34a function redundantly, as delayed flowering was observed only when all three were simultaneously disrupted. Under short day, SR34a plays a predominant role, being both necessary and sufficient to maintain normal flowering. RNA-seq and qPCR analysis revealed altered splicing of multiple flowering time regulators, including CONSTANS (CO) and FLOWERING LOCUS C (FLC). Particularly, increased production of an inhibitory CO isoform correlated with delayed flowering under long days, which was rescued by CO.1 overexpression, suggesting the phenotype was linked to CO missplicing. Overall, our findings uncover the roles of SR subfamily genes in floral transition, highlighting the physiological significance of splicing regulation in plants.

Cytoplasmic male sterility (CMS) is a trait wherein plants cannot develop normal male organs because of mitochondrial genes. In potatoes (Solanum tuberosum), reports on the relevant mitochondrial genes remain scarce. Many potato cultivars express pollen sterility caused by mitochondria, thereby limiting their use as male parents in breeding. Therefore, identifying the causal genes is crucial for potato breeding. In this study, we focused on the T/β cytoplasm type, the most prevalent cytoplasm of potato worldwide, to explore mitochondrial genes involved in CMS in potatoes. We identified a novel gene, open reading frame 320 (orf320) from potato with T/β type cytoplasm by comparing the mitochondrial genomes. The accumulation level of orf320 transcripts was drastically reduced in the anthers of a fertile potato cultivar compared with those of a sterile cultivar. Functional analysis of tomatoes showed that overexpression of orf320 with a mitochondrial transit peptide induced male sterility phenotype accompanying abnormal anther development and pollen abortion. Furthermore, an investigation of orf320 in 124 potato cultivars revealed that this gene is tightly associated with the T/β type cytoplasm and is absent from cultivars with other cytoplasm types. These findings provide evidence that orf320 is a candidate CMS-causing gene in male sterility of T/β type cytoplasm, offering valuable insights for future potato breeding.

Xylan, one of the most abundant hemicelluloses in plant cell walls, consists of β-(1 → 4)-linked xylosyl (Xyl) residues and often contains a conserved Reducing End Sequence (RES) in dicots and gymnosperms, comprising β-d-Xylp-(1 → 3)-α-l-Rhap-(1 → 2)-α-d-GalpA-(1 → 4)-d-Xylp. This tetrasaccharide has been proposed to function as a priming module ('primer hypothesis') or a termination signal ('terminator hypothesis') in xylan biosynthesis, yet its precise biochemical role remains unclear. Here, we examined whether the RES-containing oligosaccharide with one additional Xyl residue at the non-reducing end (X-RES) acts as a priming acceptor for IRREGULAR XYLEM10 (IRX10) proteins from a dicot, Arabidopsis thaliana, and a grass, Setaria viridis. Both recombinant AtIRX10L and SvIRX10 utilized fluorescently labeled X-RES and the canonical primer Xyl5 as acceptor substrates. Time-course analyses revealed that X-RES promoted a more efficient transition of +X1 to +X2 product, i.e. with minimal accumulation of +X1 product and enhanced formation of +X2 and longer products, suggesting that the RES motif facilitates seamless elongation. Consistent with these substrate-dependent differences, docking simulations showed that X-RES and its elongated form (X2-RES) bound more stably to the predicted IRX10 active site than the corresponding linear oligosaccharides Xyl5 and Xyl6. Moreover, the ability of SvIRX10 to recognize X-RES, despite RES motif not yet being detected in grass xylan, suggests that the RES-primed elongation may represent an ancestral substrate recognition in grasses. Our findings identify a structurally unique RES-containing oligosaccharide that functions as a primer in vitro, thereby extending current understanding of acceptor substrate flexibility in xylan biosynthesis. (242 words).

Comprising one of the largest plant gene families, MYB genes are major regulators of growth and development across plant tissues. Their evolutionary history is complex with recurrent gain and loss of the MYB domains, sometimes within the same multi-domained gene, creating a reticulate phylogenetic history, with various parts of the same gene having conflicting phylogenetic histories. Multiple MYB genes may co-operate or compete, thus constituting an on/off switch regulating transcription of downstream genes. We determined the phylogenetic origin of the multi-domained MYB regulators called DIVARICATA (DIV) genes, their cofactors the DRIF genes, and their competitors the LFG genes. We report that DIV arose through the fusion of two simpler MYB genes that resulted in a gene with three MYB domains (MYBA-MYB1-MYB2). The MYBA domain was later lost through a non-gradual process resulting in the two-domained MYB1-MYB2 DIV genes in green plants (including flowering plants). Further truncation of the MYB1 domain resulted in LFG genes that have only the MYB2 domain. The MYBA and the MYB2 domains were derived from the SHAQKY clade of MYB domains; the MYB1 domain and the MYBD domain of DRIF were derived from the clade associated with the SANT2 domain of ZUO1/ZRF genes. We discuss how the duplication and truncation of DIV has been repeatedly recruited in the evolution of on/off switches. Components of the DIV-based regulatory network, and their close homologs, are present in a diversity of eukaryotes suggesting that their interaction may be ancestral to a large group of eukaryotes.

Abscisic acid (ABA) is a kind of plant hormone that alleviates drought stress in many plant species. DNA methylation also plays an important role in plant drought stress tolerance. However, the relationship between ABA and DNA demethylase is unclear. Here, the action mechanism of tomato DEMETER-LIKE protein 2 (DML2) in ABA-mediated drought stress resistance was studied by mutating SlDML2. We found that the mutation of SlDML2 weakened plant growth conditions under drought stress. Additionally, the content of chlorophylls, the osmoregulatory substances (proline, soluble sugar, and soluble protein), and flavonoid were lower in sldml2-1 mutant under drought circumstances when compared with wild-type (WT) plants. However, these effects of the mutated SlDML2 couldn't be reversed by the application of ABA. Furthermore, the expression levels of SlPYL1 and SlSnRK2.4 in ABA signaling pathway were downregulated in sldml2-1 mutants under drought stress compared with WT plants. Moreover, exogenous ABA reduced the DNA methylation level and the transcriptional abundances of its regulated genes by altering SlDML2-drived DNA demethylation under drought stress. The study here declared the important role of SlDML2 in ABA-improved plant drought tolerance, which may facilitate studies concerning ABA and DNA demethylation in the future.

Excess light during photosynthesis induces harmful reactive oxygen species. As a defense mechanism, plants possess rapidly reversible energy-dependent quenching (qE), in which excitation energy in the photosystem II antenna is dissipated as heat when absorbed light is in excess. In the Viridiplantae, qE is regulated by two key proteins: LHCSR and PsbS. LHCSR is widely conserved in green algae and bryophytes, early-diverging land plants. In contrast, PsbS functions as the major qE regulator in vascular plants, reflecting an evolutionary shift from LHCSR to PsbS. Despite its importance in vascular plants, the function of PsbS remains poorly understood in green algae, especially in streptophyte algae, the closest relatives of land plants. To examine PsbS activity in streptophyte algae, we focused on Chlorokybus cerffii and Klebsormidium nitens, which represent early-diverging lineages in Streptophyta. We expressed their PsbS genes in the PsbS-deficient Arabidopsis thaliana mutant npq4, along with PsbS genes from A. thaliana and Chlamydomonas reinhardtii. All PsbS genes complemented the npq4 mutant phenotype with varying degrees of efficiency depending on the protein expression levels. Moreover, the qE efficiencies per unit of PsbS protein in the algal PsbS transformants were equal to or higher than those of AtPsbS transformants. The results suggest that PsbS activity as a qE regulator was already established in the common ancestor of streptophytes prior to land plant colonization.

Single-cell RNA sequencing (scRNA-seq) enables high-resolution transcriptome analysis, enabling the study of cellular heterogeneity beyond bulk transcriptomics. However, plant science lags animal science in the field largely due to limited sssssssssmarker genes. This study developed PscOA (http://sdau.biodb.com.cn/pscoa/), a plant scRNA-seq marker gene database with 39 347 marker genes. PscOA integrates BLAST for homology-based marker gene mining, and SCSA for cell type annotation, complemented by visualization tools. Case studies in A. thaliana and P. alba demonstrate the potential of cell type annotation in PscOA. Leveraging A. thaliana marker genes from PscOA, we predict 258 potential markers in Nicotiana tabacum, showcasing its marker gene discovery potential for specific species. Differential expression analysis under stress reveals common and diverse strategies at the single-cell level, offering insights into plant cell type diversity and function. Altogether, PscOA serves as a valuable repository for original scRNA-seq analysis in plant science, deepening the understanding of plant cellular transcriptome.

Camelina sativa is an ancient native oilseed species characterized by broad environmental adaptability, low-input requirements and tolerance to multiple stresses. Its potential use in agroecological transition with double cropping systems could be improved by breeding a shorter life cycle. However, this strategy should not compromise its resilience to stresses as well as its metabolite profiles and plasticity. The impact of flowering time on drought stress response and seed quality was evaluated in six camelina edited mutants, carrying combinatory mutations on the flowering time genes SVP, TFL1, LHP1, ELF3 and FLC and leading to a range of flowering precocity and shoot architecture changes. We characterized the phenotype of these mutants in response to early and late drought and showed that their flowering time was not strongly altered contrary to branching and yield. Untargeted metabolomic demonstrated that in contrary to the lipidomic profile, the plasticity of the specialized metabolite was strongly modulated by drought in all genotypes. Specialized metabolite profile of the mutant seeds showed distinct pattern in response to drought with constitutive stress response of the bushy mutants in control condition including differences in antioxidant content such as glutathione, isoquercetrin, and coumaroyl quinic acid. Metabolite profiling in leaves also showed specific metabolic signatures of some mutants but with lower metabolite diversity than in seeds. Including additional genotypes with distinct flowering time, we identified metabolites correlating with this trait, such as vitamin B2 and kynurenic acid in seeds. These metabolites could be used as predictive markers of flowering time.