Plant Physiology最新文献

Inositol phosphates (InsP) play diverse signaling roles in regulating development, phosphate sensing, and energy metabolism. Here, we identify 4 maize (Zea mays) mutants, big embryo 2 (bige2), big embryo 3 (bige3), big embryo 4 (bige4), and low phytic acid 1 (lpa1), that show enlargement of the embryo at the expense of endosperm. Bige2 (identical to Lpa2), Bige3 (identical to Lpa3), and Bige4 genes encode inositol phosphate triphosphokinase (ITPK) and mono-inositol phosphate kinase (MIK), both of which catalyze lipid-independent InsP biosynthesis, and inositol polyphosphate kinase (IPK2) in the lipid-dependent InsP pathway, respectively. Lpa1 encodes a tonoplast InsP6 transporter. InsP pathway mutants primarily affect scutellum growth, with each mutant exhibiting a distinct spatial pattern of cell enlargement and/or cell number. Genetic epistasis and transcriptome analyses reveal overlapping and nonredundant roles of lipid-independent and -dependent pathways in regulation of embryo development. Strikingly, ectopic expression of endosperm-specific genes in lpa2-bige2 and bige4 embryos reveals a shift toward endosperm organ identity. We identify a network of NAC transcription factors implicated in shaping lpa2-bige2 and bige4 transcriptomes. Disruption of lipid-independent InsP biosynthesis in lpa2-bige2 is associated with upregulation of a subnetwork of SOG1-related NAC proteins linked to DNA damage repair and endoreduplication. The lpa2-bige2 phenotype is fully suppressed by lpa1, suggesting that a block in InsP6 uptake into the vacuole restores signaling by cytosolic InsP intermediates. Together, these results establish a genetic framework for dissecting complex roles of InsP signaling in seed development.

Plants possess conserved immune systems to defend against herbivorous insects. In response, insects secrete saliva to manipulate host cell biology, with many salivary proteins being species-specific. The mechanisms by which different insects, armed with distinct salivary components, counteract the conserved plant immune systems are not well understood. Here, we describe how 2 salivary effectors from the brown planthopper Nilaparvata lugens and the bean bug Riptortus pedestris target pathogenesis-related germin-like proteins (GLPs) in rice and soybean. In N. lugens, NlGTSP is expressed exclusively in the salivary glands and is secreted into host plants during feeding. Its knockdown significantly reduces phloem feeding and reproduction, whereas overexpression in rice enhances insect performance and rescues NlGTSP deficiency. NlGTSP partly modulates defenses by interacting with plant GLPs and inhibiting their enzymatic activity. In R. pedestris, the salivary protein RpGDSP lacks sequence or structural similarity to NlGTSP but also targets GLPs, promoting their degradation via the ubiquitin pathway to enhance feeding. Collectively, our findings reveal a functional analogy between salivary effectors from different insects that regulate core plant defense genes through distinct mechanisms.

In plants, both developmental processes and environmental responses are spatiotemporally regulated by an assembly of signaling molecules such as hormones, secondary metabolites, and ions. The ability of these signaling molecules to move within and across plant tissues is essential for various developmental cues. However, the characterization of transported signaling molecules and their translocation mechanisms is difficult due to the functional redundancy of plant genomes and shortcomings in methodologies. Here, we report our development of the Multi Targeted AmiRNA Cell type-specific Transportome-scale (mTACT) toolbox, which can be used to reveal phenotypic plasticity in plants. mTACT is based on a large set of artificial microRNAs (amiRNAs), each designed to optimally target multiple members of a particular gene family encoding transporter proteins. In total, the mTACT toolbox includes 5,565 amiRNAs, targeting 81.7% of the Arabidopsis (Arabidopsis thaliana) transportome. The amiRNA library can be driven under 12 cell type-specific promoters, allowing the design of spatial-specific genetic screens. mTACT is further divided into 8 sublibraries of amiRNAs targeting a functionally defined protein class. A proof-of-concept screen validated the mTACT approach by identifying phenotypes linked to both known and unidentified genes. With the ability to overcome functional redundancy in a transportome-scale, cell type-specific manner, the mTACT toolbox will allow the plant research community to study previously hidden genetic factors required for long- and short-distance translocation of signaling molecules.

Rice (Oryza sativa) indica and japonica inter-subspecific hybrids hold significant potential for increasing yields. However, differences in diurnal flower-opening time (DFOT) between the 2 subspecies limit the effective exploitation of this heterosis. Additionally, the timing of post-anthesis glume closure (PAGC) affects both hybrid seed yield and quality. Despite their importance, the molecular mechanisms underlying these processes, particularly glume closure, remain poorly understood. In this study, we identify OsAIM1 as a pivotal regulator of both DFOT and PAGC in rice. The aim1-2 mutant exhibits delayed DFOT and impaired PAGC while maintaining normal floret structure, emphasizing its crucial role in floret dynamics. OsAIM1 is highly expressed in lodicules and encodes a peroxisome-localized multifunctional protein. Functional analyses reveal that OsAIM1 regulates lodicule swelling during floret opening and withering post-anthesis, processes essential for glume movement. We further demonstrate that OsAIM1-dependent jasmonic acid biosynthesis is indispensable for coordinating floret opening and closure and influences sugar transport to ensure proper lodicule dynamics. Importantly, natural variation in the OsAIM1 coding region contributes to DFOT divergence between japonica and indica subspecies, providing a molecular basis for their asynchronous flowering. These findings establish OsAIM1 as a key regulator of floret dynamics and a promising molecular target for synchronizing flowering in hybrid rice production.

Extracellular vesicles (EVs) produced by Arabidopsis (Arabidopsis thaliana) plants are highly heterogeneous in protein content. To understand the origins of plant EV heterogeneity, we used an unbiased proximity labeling approach to identify proteins and pathways involved in the secretion of distinct EV subpopulations. Proximity labeling, co-immunoprecipitation, and fluorescence microscopy in Nicotiana benthamiana all indicated a general role in EV secretion for EXO70 proteins (a subunit of the exocyst complex) and the immune-related protein RPM1-INTERACTING PROTEIN4 (RIN4). To confirm these hypotheses, we assessed the impact of mutations in various EXO70 family genes and in RIN4 on EV release, as well as mutations in additional genes known to regulate endomembrane trafficking and secretion. Mutation of EXO70E1, EXO70E2 or STOMATAL CYTOKINESIS DEFECTIVE1 (SCD1; a GTP-exchange factor for RabE GTPases) reduced secretion of EVs marked by TETRASPANIN8 (TET8), PENETRATION1 (PEN1), and PATELLIN1 (PATL1), indicating that these proteins are generally required for EV secretion. In contrast, mutation of RIN4 reduced levels of TET8+ and PEN1+ EVs, but not PATL+ EVs. Mutation of the small GTPase gene RABA2a specifically affected PEN1+ EV secretion, while mutations in AUTOPHAGY PROTEIN5 (ATG5) and VAMP-ASSOCIATED PROTEIN27 (VAP27) specifically affected TET8+ EV secretion. Lastly, we found that exo70 family mutants are more susceptible to infection with the fungal pathogen Colletotrichum higginsianum, underlining the importance of secretion for plant immunity. Together, our results unravel some of the complex mechanisms that give rise to EV subpopulations in plants.

Recurrent drought stress seriously threatens plant growth and crop production, but plant drought adaptation often comes at a yield penalty, known as the growth-defense trade-off. Therefore, deciphering the mechanisms of trade-off between plant growth and drought tolerance is of great importance for plant survival and crop yield in fluctuating environments. Our recent studies have shown that U-box E3 ubiquitin ligase OsPUB33 reduces rice (Oryza sativa L.) grain yield via ubiquitination and degradation of the transcription factor OsNAC120, a positive regulator of grain size, whereas OsNAC120 compromises rice drought tolerance through transcriptionally repressing drought-responsive genes. In the present study, we found that the OsPUB33-OsNAC120 module acts as a molecular switch between drought response and growth recovery in rice. OsPUB33 enhanced ABA-induced drought tolerance, and its protein abundance rapidly increased at the early stage of drought stress and returned to normal at the rehydration stage, whereas OsNAC120 acted oppositely. Genetic evidence showed that OsPUB33 and OsNAC120 regulate rice drought response through a common pathway. Notably, OsNAC120 phosphorylation mediated by OsSAPK9, a key SnRK2 kinase in ABA signaling, enhanced its interaction with OsPUB33, thus promoting OsNAC120 ubiquitination for degradation under drought stress and increasing rice drought tolerance. When drought stress was relieved, OsPUB33 abundance declined, while OsNAC120 levels increased, consequently achieving growth recovery. These findings indicate that the OsPUB33-OsNAC120 module, which is controlled by OsSAPK9, is a molecular switch between the drought response and growth recovery, revealing a key mechanism of plant growth regulation under drought stress in rice.

The physiological role of the plastidial photosynthetic complex I (formerly NAD(P)H dehydrogenase-like complex, NDH) within the electron transport chain of plants remains intriguing. While the NDH complex shares homology with complex I, a key component of the respiratory electron transport chain, electron transport rates through the NDH complex in thylakoids are relatively low. In this study, we used a structure-function approach and mutated the plastid genome-encoded ndhF gene to abolish the NdhF proton channel of the NDH complex. These mutations led to loss of plastoquinone reductase activity, indicating tight coupling between the proton and electron transfer reactions within NDH. Additionally, loss of the transverse helix of NdhF led to loss of the NDH complex, suggesting that this region of the NdhF subunit is required for complex stability. In agreement with previous studies using ndh knockout mutants, loss of NDH complex activity did not result in measurable changes in rates of steady-state cyclic electron flow. However, all mutants displayed a shift in the sensitivity of pH-dependent feedback regulation of the photosystem II antennae to total protonmotive force (pmf), indicating a possible defect in either stromal redox state or pmf distribution into ΔpH and Δψ.

Light and subterranean darkness play a crucial role in early plant development which guide seamless progression from a dormant seed to a well-established seedling. In seed plants crosstalk between light and hormone signaling pathways optimizes seed germination. This is followed by etiolated growth characterized by the formation of a long hypocotyl and closed cotyledons forming apical hook. These etiolated structures facilitate the efficient emergence of seedlings from underneath the soil. Upon emergence, exposure to light promotes the de-etiolation process, characterized by inhibition of hypocotyl elongation and formation of open and green cotyledons. The early developmental steps in a plant's life-cycle which include seed germination and post-germinative seedling establishment, are the most stress sensitive stages. To acclimatize with the changing environment plants must activate stress resilience pathways. Recent studies shed light on how light and dark regulated factors modulate responses to combat various abiotic stresses including high temperature, high-intensity light, UV-B radiation and salinity stress. Plant biologists have traditionally examined plant-environment interactions utilizing two complementary but distinct approaches. Developmental biology has focused on the interplay of external influences such as light, temperature and endogenous cues like phytohormones to modulate plant development. Stress biology, in contrast, has studied how various physiological and molecular processes are regulated in response to environmental stress and leading to the plant's ability to adapt. Here we link these two concepts by demonstrating how light-controlled developmental-programs are tightly connected to stress-responsive pathways. These interconnected systems provide flexibility and resilience to plants to survive and evolve under dynamic environments.