The Plant Journal最新文献

The tea plant (Camellia sinensis) is a perennial green plant, and its tender leaves are rich in secondary metabolites, such as theanine. Ethylamine (EA), a small amine, is an important prerequisite for theanine synthesis. However, beyond its involvement in theanine synthesis, the other physiological functions of EA in tea plants remain unknown. In vitro experiments indicate that EA may function as scavengers of reactive oxygen species (ROS) to protect the plant against damage caused by osmotic stress. Additionally, a significant correlation between EA levels and osmotic tolerance has been observed in different tea varieties. From the results, alanine decarboxylase (CsAlaDC)-silenced tea leaves and overexpressed CsAlaDC Arabidopsis thaliana lines decreased and increased EA levels, respectively, and mediated ROS homeostasis, thus exhibiting a sensitive and tolerant phenotype. In addition, the transcription factor (TF) CsCBF4 was functionally identified, which can directly bind to the CsAlaDC promoter. CsCBF4-silenced tea leaves significantly reduced the expression levels of CsAlaDC and in turn EA content, resulting in excess ROS accumulation and an osmotic-sensitive phenotype. Taken together, these results established a new regulatory module consisting of CBF4-CsAlaDC responsible for EA accumulation and ROS homeostasis in response to osmotic stress.

Nourishing the embryo with endosperm and enclosing both embryo and endosperm in the seed coat are two important evolutionary innovations. Seed coat is conventionally viewed as a protective layer that functions after the seed has matured. Here, we challenge this notion by showing that a subregion of the seed coat, termed the chalazal seed coat (CZSC), is geared to gate seed nutrition loading in developing seeds. The CZSC develops the coordinative system comprising the apoplastic isolation, mediated by the restricted suberization, and the active transport, mediated by the specific expression of a variety of transporters, at as early as the globular embryo stage in both Arabidopsis and soybean seeds. This coordinated system in the CZSC disrupts the vascular continuum to the maternal tissues and forces the nutrient transport into selective and active absorption. We further reveal that the precision of the spatiotemporal suberin deposition and transporter expression is controlled by the regulatory hierarchy of SHR-MYBs cascades. Our results provide a mechanistic insight into the assimilate accumulation in dicot seeds.

Algae such as diatoms and haptophytes have distinct photosynthetic pigments from plants, including a novel set of carotenoids. This includes a primary xanthophyll cycle comprised of diadinoxanthin and its de-epoxidation product diatoxanthin that enables the switch between light harvesting and non-photochemical quenching (NPQ)-mediated dissipation of light energy. The enzyme responsible for the reversal of this cycle was previously unknown. Here, we identified zeaxanthin epoxidase 3 (ZEP3) from Phaeodactylum tricornutum as the candidate diatoxanthin epoxidase. Knocking out the ZEP3 gene caused a loss of rapidly reversible NPQ following saturating light exposure. This correlated with the maintenance of high concentrations of diatoxanthin during recovery in low light. Xanthophyll cycling and NPQ relaxation were restored via complementation of the wild-type ZEP3 gene. The zep3 knockout strains showed reduced photosynthetic rates at higher light fluxes and reduced specific growth rate in variable light regimes, likely due to the mutant strains becoming locked in a light energy dissipation state. We were able to toggle the level of NPQ capacity in a time and dose dependent manner by placing the ZEP3 gene under the control of a β-estradiol inducible promoter. Identification of this gene provides a deeper understanding of the diversification of photosynthetic control in algae compared to plants and suggests a potential target to improve the productivity of industrial-scale cultures.

Dormancy is an essential characteristic that enables seeds to survive in unfavorable conditions while germinating when conditions are favorable. Myosin-binding proteins (MyoBs) assist in the movement of organelles along actin microfilaments by attaching to both organelles and myosins. In contrast to studies on yeast and metazoans, research on plant MyoBs is still in its early stages and primarily focuses on tip-growing cells. In this study, we found that Arabidopsis MyoB13 is highly expressed in dry mature seeds. The myob13 mutant, created using CRISPR/Cas9, exhibits a preharvest sprouting phenotype, which can be mitigated by after-ripening treatment, indicating that MyoB13 plays a positive role in primary seed dormancy. Furthermore, we show that MyoB13 negatively regulates ABA biosynthesis and signaling pathways. Notably, the expression of MyoB13 orthologs from maize and soybean can completely restore the phenotype of the Arabidopsis myob13 mutant, suggesting that the function of MyoB13 in ABA-induced seed dormancy is evolutionarily conserved. Therefore, the functional characterization of MyoB13 offers an additional genetic resource to help prevent vivipary in crop species.

Ozone (O₃) is an oxidative pollutant that significantly threatens plant development and ecological dynamics. The present study explores the impact of O₃ on Moringa (Moringa oleifera) ecotypes when exposed to ambient and elevated O₃ levels. Elevated O₃ concentrations resulted in significant reductions in total biomass for all ecotypes. Photosynthetic parameters, including stomatal conductance (g_sto), CO₂ assimilation (P_n), and carboxylation efficiency (K), decreased under elevated O₃ in some ecotypes, indicating a detrimental effect on carbon assimilation. Nonstructural carbohydrate (NSC) levels in roots varied among ecotypes, with significant reductions in starch content observed under elevated O₃, suggesting a potential shift towards soluble sugar accumulation and reallocation for antioxidant defense. Secondary metabolite analysis revealed increased polyphenol production, particularly quercetin derivatives, under elevated O₃ in specific ecotypes, highlighting their role in mitigating oxidative stress. Interestingly, the glucosinolate content also varied, with some ecotypes exhibiting increased levels, suggesting a complex regulatory mechanism in response to O₃ exposure. The study underscores the intrinsic variability among Moringa ecotypes in response to O₃ stress, emphasizing the importance of genetic diversity for adaptation. The findings indicate that Moringa's metabolic plasticity, including shifts in NSC and SM production, plays a crucial role in its defense mechanisms against O₃-induced oxidative stress. These insights are vital for optimizing the cultivation and utilization of Moringa in diverse environmental conditions, particularly in regions with elevated O₃ levels.

Plants direct substantial amounts of carbon toward the biosynthesis of aromatic amino acids (AAAs), particularly phenylalanine to produce lignin and other phenylpropanoids. Yet, we have a limited understanding of how plants regulate AAA metabolism, partially because of a scarcity of robust analytical methods. Here, we established a simplified workflow for simultaneous quantification of AAAs and their pathway intermediates from plant tissues, based on extraction at two alternative pH and analysis by Zwitterionic hydrophilic interaction liquid chromatography coupled to mass spectrometry. This workflow was then used to analyze metabolic responses to elevated or reduced carbon flow through the shikimate pathway in plants. Increased flow upon expression of a feedback-insensitive isoform of the first shikimate pathway enzyme elevated all AAAs and pathway intermediates, especially arogenate, the last common precursor within the post-chorismate pathway of tyrosine and phenylalanine biosynthesis. Additional overexpression of an arogenate dehydrogenase enzyme increased tyrosine levels and depleted phenylalanine and arogenate pools; however, the upstream shikimate pathway intermediates remained accumulated at high levels. Glyphosate treatment, which restricts carbon flow through the shikimate pathway by inhibiting its penultimate step, led to a predictable accumulation of shikimate and other precursors upstream of its target enzyme but also caused an unexpected accumulation of downstream metabolites, including arogenate. These findings highlight that the shikimate pathway and the downstream post-chorismate AAA pathways function as independently regulated modules in plants. The method developed here paves the way for a deeper understanding of the shikimate and AAA biosynthetic pathways in plants.

Lipid droplets (LDs) are unusual organelles that have a phospholipid monolayer surface and a hydrophobic matrix. In oilseeds, this matrix is nearly always composed of triacylglycerols (TGs) for efficient storage of carbon and energy. Various proteins play a role in their assembly, stability and turnover, and even though the major structural oleosin proteins in seed LDs have been known for decades, the factors influencing LD formation and dynamics are still being uncovered mostly in the "model oilseed" Arabidopsis. Here we identified several key LD biogenesis proteins in the seeds of pennycress, a potential biofuel crop, that were correlated previously with seed oil content and characterized here for their participation in LD formation in transient expression assays and stable transgenics. One pennycress protein, the lipid droplet associated protein-interacting protein (LDIP), was able to functionally complement the Arabidopsis ldip mutant, emphasizing the close conservation of lipid storage among these two Brassicas. Moreover, loss-of-function ldip mutants in pennycress exhibited increased seed oil content without compromising plant growth, raising the possibility that LDIP or other LD biogenesis factors may be suitable targets for improving yields in oilseed crops more broadly.

Land plants have evolved a hydrophobic cuticle on the surface of aerial organs as an adaptation to ensure survival in terrestrial environments. Cuticle is mainly composed of lipids, namely cutin and intracuticular wax, with epicuticular wax deposited on plant surface. The composition and permeability of cuticle have a large influence on its ability to protect plants against drought stress. However, the regulatory mechanisms underlying cuticular wax biosynthesis in response to drought stress have not been fully elucidated. Here, we identified three AP2/ERF transcription factors (DREB26/ERF12, ERF13 and ERF14) involved in the regulation of water permeability of the plant surface. Transmission electron microscopy revealed thicker cuticle on the leaves of DREB26-overexpressing (DREB26OX) plants, and thinner cuticle on the leaves of transgenic plants expressing SRDX repression domain-fused DREB26 (DREB26SR). Genes involved in cuticular wax formation were upregulated in DREB26OX and downregulated in DREB26SR. The levels of very-long chain (VLC) alkanes, which are a major wax component, increased in DREB26OX leaves and decreased in DREB26SR leaves. Under dehydration stress, water loss was reduced in DREB26OX and increased in DREB26SR. The erf12/13/14 triple mutant showed delayed growth, decreased leaf water content, and reduced drought-inducible VLC alkane accumulation. Taken together, our results indicate that the DREB26/ERF12 and its closed family members, ERF13 and ERF14, play an important role in cuticular wax biosynthesis in response to drought stress. The complex transcriptional cascade involved in the regulation of cuticular wax biosynthesis under drought stress conditions is discussed.

Previous research on the ripening process of many fruit crop varieties typically involved analyses of the conserved genetic factors among species. However, even for seemingly identical ripening processes, the associated gene expression networks often evolved independently, as reflected by the diversity in the interactions between transcription factors (TFs) and the targeted cis-regulatory elements (CREs). In this study, explainable deep learning (DL) frameworks were used to predict expression patterns on the basis of CREs in promoter sequences. We initially screened potential lineage-specific CRE-TF interactions influencing the kiwifruit ripening process, which is triggered by ethylene, similar to the corresponding processes in other climacteric fruit crops. Some novel regulatory relationships affecting ethylene-induced fruit ripening were identified. Specifically, ABI5-like bZIP, G2-like, and MYB81-like TFs were revealed as trans-factors modulating the expression of representative ethylene signaling/biosynthesis-related genes (e.g., ACS1, ERT2, and ERF143). Transient reporter assays and DNA affinity purification sequencing (DAP-Seq) analyses validated these CRE-TF interactions and their regulatory relationships. A comparative analysis with co-expression networking suggested that this DL-based screening can identify regulatory networks independently of co-expression patterns. Our results highlight the utility of an explainable DL approach for identifying novel CRE-TF interactions. These  imply that fruit crop species may have evolved lineage-specific fruit ripening-related cis-trans regulatory networks.

Plant height can be an indicator of plant health across environments and used to identify superior genotypes. Typically plant height is measured at a single timepoint when plants reach terminal height. Evaluating plant height using unoccupied aerial vehicles allows for measurements throughout the growing season, facilitating a better understanding of plant-environment interactions and the genetic basis of this complex trait. To assess variation throughout development, plant height data was collected from planting until terminal height at anthesis (14 flights 2018, 27 in 2019, 12 in 2020, and 11 in 2021) for a panel of ~500 diverse maize inbred lines. The percent variance explained in plant height throughout the season was significantly explained by genotype (9-48%), year (4-52%), and genotype-by-year interactions (14-36%) to varying extents throughout development. Genome-wide association studies revealed 717 significant single nucleotide polymorphisms associated with plant height and growth rate at different parts of the growing season specific to certain phases of vegetative growth. When plant height growth curves were compared to growth curves estimated from canopy cover, greater Fréchet distance stability was observed in plant height growth curves than for canopy cover. This indicated canopy cover may be more useful for understanding environmental modulation of overall plant growth and plant height better for understanding genotypic modulation of overall plant growth. This study demonstrated that substantial information can be gained from high temporal resolution data to understand how plants differentially interact with the environment and can enhance our understanding of the genetic basis of complex polygenic traits.