New Phytologist最新文献

N⁶-methyladenosine (m⁶A) RNA modification is the most prevalent messenger RNA (mRNA) modification in eukaryotes and plays critical roles in the regulation of gene expression. m⁶A is a reversible RNA modification that is deposited by methyltransferases (writers) and removed by demethylases (erasers). The function of m⁶A erasers in plants is highly diversified and their roles in cereal crops, especially in reproductive development essential for crop yield, are largely unknown. Here, we demonstrate that rice OsALKBH5 acts as an m⁶A demethylase required for the normal progression of male meiosis. OsALKBH5 is a nucleo-cytoplasmic protein, highly enriched in rice anthers during meiosis, that associates with P-bodies and exon junction complexes, suggesting that it is involved in regulating mRNA processing and abundance. Mutations of OsALKBH5 cause reduced double-strand break (DSB) formation, severe defects in DSB repair, and delayed meiotic progression, leading to complete male sterility. Transcriptome analysis and m⁶A profiling indicate that OsALKBH5-mediated m⁶A demethylation stabilizes the mRNA level of multiple meiotic genes directly or indirectly, including several genes that regulate DSB formation and repair. Our study reveals the indispensable role of m⁶A metabolism in post-transcriptional regulation of meiotic progression in rice.

It is well-known that the mycorrhizal type of plants correlates with different modes of nutrient cycling and availability. However, the differences in drought tolerance between arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) plants remains poorly characterized. We synthesized a global dataset of four hydraulic traits associated with drought tolerance of 1457 woody species (1139 AM and 318 EcM species) at 308 field sites. We compared these traits between AM and EcM species, with evolutionary history (i.e. angiosperms vs gymnosperms), water availability (i.e. aridity index) and biomes considered as additional factors. Overall, we found that evolutionary history and biogeography influenced differences in hydraulic traits between mycorrhizal types. Specifically, we found that (1) AM angiosperms are less drought-tolerant than EcM angiosperms in wet regions or biomes, but AM gymnosperms are more drought-tolerant than EcM gymnosperms in dry regions or biomes, and (2) in both angiosperms and gymnosperms, variation in hydraulic traits as well as their sensitivity to water availability were higher in AM species than in EcM species. Our results suggest that global shifts in water availability (especially drought) may alter the biogeographic distribution and abundance of AM and EcM plants, with consequences for ecosystem element cycling and ultimately, the land carbon sink.

Long terminal repeat retroelements (LTR-REs) have profound effects on DNA methylation and gene regulation. Despite the vast abundance of LTR-REs in the genome of Moso bamboo (Phyllostachys edulis), an industrial crop in underdeveloped countries, their precise implication of the LTR-RE mobility in stress response and development remains unknown. We investigated the RNA and DNA products of LTR-REs in Moso bamboo under various developmental stages and stressful conditions. Surprisingly, our analyses identified thousands of active LTR-REs, particularly those located near genes involved in stress response and developmental regulation. These genes adjacent to active LTR-REs exhibited an increased expression under stress and are associated with reduced DNA methylation that is likely affected by the induced LTR-REs. Moreover, the analyses of simultaneous mapping of insertions and DNA methylation showed that the LTR-REs effectively alter the epigenetic status of the genomic regions where they inserted, and concomitantly their transcriptional competence which might impact the stress resilience and growth of the host. Our work unveils the unusually strong LTR-RE mobility in Moso bamboo and its close association with (epi)genetic changes, which supports the co-evolution of the parasitic DNAs and host genome in attaining stress tolerance and developmental robustness.

Light is essential not only for photosynthesis but also for the regulation of various physiological and developmental processes in plants. While the mechanisms by which light regulates transcription and protein stability are well established, the effects of light on RNA methylation and their subsequent impact on plant growth and development are less understood. Upon exposure to blue light, the photoreceptor cryptochromes form nuclear speckles or nuclear bodies, termed CRY photobodies. The CRY2 photobodies undergo light-induced homo-oligomerization and liquid-liquid phase separation (LLPS), which are crucial for their physiological activity. Recent studies have proposed that blue light-induced CRY2 LLPS increases the local concentration or directly enhances the biochemical activities of RNA N6-methyladenosine (m⁶A) methyltransferases, thus, to regulate circadian clock and maintain Chl homeostasis through processes of RNA decay or translation. This review aimed to elucidate the functions of CRY2 and LLPS in RNA methylation, focusing on the light-controlled reversible phase transitions regulon and the outstanding questions that remain in RNA methylation.

Plant MADS-box proteins are vital for abiotic stress tolerance, yet their mechanisms for responding to drought remain poorly understood. Here, we investigated the drought tolerance mechanism of a MADS-box protein (BpMADS11) from birch (Betula platyphylla) using immunoprecipitation, Western blotting, yeast two-hybrid, yeast one-hybrid, ChIP, RNA-seq, and dual-luciferase assays to explore post-translational modifications, protein interactions, and gene regulation. Birch plants overexpressing BpMADS11 exhibited enhanced drought tolerance, while knockout lines displayed reduced tolerance. Under drought conditions, BpMADS11 interacts with protein phosphatase 2C22 (BpPP2C22), which dephosphorylates BpMADS11. Birch plants that overexpress BpMADS11 and lack BpPP2C22 show significantly reduced drought tolerance compared with those that only overexpress BpMADS11. BpMADS11 regulates the expression of BpERF61 by binding to CArG-box in its promoter. The dephosphorylated BpMADS11 exhibits increased DNA binding ability and increased expression of BpERF61. Like BpMADS11, birch plants overexpressing BpERF61 show improved drought tolerance, while those with BpERF61 knockout exhibit decreased tolerance. BpERF61 binds to specific DNA motifs including 'CACGTG' (G-box), 'GGGCCCC', and 'TTGGAT' to regulate the genes related to drought stress. Collectively, BpMADS11 undergoes dephosphorylation through its interaction with BpPP2C22, prompting the expression of BpERF61. Subsequently, BpERF61 regulates downstream genes by binding to specific DNA motifs, thereby enhancing drought tolerance.

Phosphate (P_i) plays a key role in plant growth and development. Hence, plants display a range of adaptations to acquire it, including changes in root system architecture (RSA). Whether P_i triggers directional root growth is unknown. We investigated whether Arabidopsis roots sense P_i and grow towards it, that is whether they exhibit phosphotropism. While roots did exhibit a clear P_i-specific directional growth response, it was, however, always to the left, independent of the direction of the P_i gradient. We discovered that increasing concentrations of KH₂PO₄, trigger a dose-dependent skewing response, in both primary and lateral roots. This phenomenon is P_i-specific - other nutrients do not trigger this - and involves the reorganisation of the microtubule cytoskeleton in epidermal cells of the root elongation zone. Higher P_i levels promote left-handed cell file rotation that results in right-handed, clockwise, root growth and leftward skewing as a result of the helical movement of roots (circumnutation). Our results shed new light on the role of P_i in root growth, and may provide novel insights for crop breeding to optimise RSA and P-use efficiency.

RNA-dependent RNA Polymerases (RdRPs) synthesize double-stranded RNA (dsRNA) from a single-stranded RNA (ssRNA) template. In plants, dsRNAs produced by RdRPs can be further processed into small interfering RNA (siRNAs) with different lengths, ranging from 21 to 24 nucleotides (nt). These siRNAs play a pivotal role in various biological processes, including antiviral responses, transposable elements silencing, DNA methylation, and the regulation of plant reproduction and development. Recent research has reported significant progress in uncovering the molecular mechanisms of plant RNA-DEPENDENT RNA POLYMERASE 2 (RDR2), a representative RdRP involved in the RNA-directed DNA methylation (RdDM) pathway. These discoveries provide a molecular basis underlying the principles of RdRP function and offer insights into potential advancements in crop breeding and antiviral defense strategies.

Carbon isotope discrimination (∆) in leaf biomass (∆_BL) and tree rings (∆_TR) provides important proxies for plant responses to climate change, specifically in terms of intrinsic water-use efficiency (iWUE). However, the nonphotosynthetic ¹²C/¹³C fractionation in plant tissues has rarely been quantified and its influence on iWUE estimation remains uncertain. We derived a comprehensive, ∆ based iWUE model (iWUE_com) which includes nonphotosynthetic fractionations (d) and characterized tissue-specific d-values based on global compilations of data of ∆_BL, ∆_TR and real-time ∆ in leaf photosynthesis (∆_online). iWUE_com was further validated with independent datasets. ∆_BL was larger than ∆_online by 2.53‰, while ∆_BL and ∆_TR showed a mean offset of 2.76‰, indicating that ∆_TR is quantitatively very similar to ∆_online. Applying the tissue-specific d-values (d_BL = 2.5‰, d_TR = 0‰), iWUE estimated from ∆_BL aligned well with those estimated from ∆_TR or gas exchange. ∆_BL and ∆_TR showed a consistent iWUE trend with an average CO₂ sensitivity of 0.15 ppm ppm^-1 during 1975-2015. Accounting for nonphotosynthetic fractionations improves the estimation of iWUE based on isotope records in leaf biomass and tree rings, which is ultimate for inferring changes in carbon and water cycles under historical and future climate.

Soil moisture shapes ecological patterns and processes, but it is difficult to continuously measure soil moisture variability across the landscape. To overcome these limitations, soil moisture is often bioindicated using community-weighted means of the Ellenberg indicator values of vascular plant species. However, the ecology and distribution of plant species reflect soil water supply as well as atmospheric water demand. Therefore, we hypothesized that Ellenberg moisture values can also reflect atmospheric water demand expressed as a vapour pressure deficit (VPD). To test this hypothesis, we disentangled the relationships among soil water content, atmospheric vapour pressure deficit, and Ellenberg moisture values in the understory plant communities of temperate broadleaved forests in central Europe. Ellenberg moisture values reflected atmospheric VPD rather than soil water content consistently across local, landscape, and regional spatial scales, regardless of vegetation plot size, depth as well as method of soil moisture measurement. Using in situ microclimate measurements, we discovered that forest plant indicator values for moisture reflect an atmospheric VPD rather than soil water content. Many ecological patterns and processes correlated with Ellenberg moisture values and previously attributed to soil water supply are thus more likely driven by atmospheric water demand.