Nature Plants最新文献

Biodiversity is increasingly threatened by local extinction under global climate change. This may reflect direct effects of climate on poorly adapted native species or increased impacts of exotic species in these conditions, but their relative importance is poorly understood. By examining global occurrence records of 142 plant species found in the Yangtze River Valley, we found that the climatic niches of exotic species differed from those of natives, mainly reflecting exotics being most common in warmer, drier and more isothermal climates in their native ranges. These differences in climatic niches, especially temperature, predicted invasion intensity in 459 plots along a 1,800-km transect in the Yangtze River Valley. On the basis of this strong match between model predictions and field survey results, we predict that invasions will probably be more intense in future climatic conditions, especially from warming at the coldest sites. The direct negative effect of warming on native diversity was larger than the indirect effects mediated through increased invasions. However, moderate invasion increased communities’ overall species diversity. More broadly, our study highlights the role of exotic species in the ecological response of regional biodiversity to global climate change.

SUMOylation—the attachment of a small ubiquitin-like modifier (SUMO) to target proteins—plays roles in controlling plant growth, nutrient signalling and stress responses. SUMOylation studies in plants are scarce because identifying SUMOylated proteins and their sites is challenging. To date, only around 80 SUMOylation sites have been identified. Here we introduce lysine-null SUMO1 into the Arabidopsis sumo1 sumo2 mutant and establish a two-step lysine-null SUMO enrichment method. We identified a site-specific SUMOylome comprising over 2,200 SUMOylation sites from 1,300 putative acceptors that function in numerous nuclear processes. SUMOylation marks occur on several motifs, differing from the canonical ψKxE motif in distant eukaryotes. Quantitative comparisons demonstrate that SUMOylation predominantly enhances the stability of SUMO1 acceptors. Our study delivers a highly sensitive and efficient method for site-specific SUMOylome studies and provides a comprehensive catalogue of Arabidopsis SUMOylation, serving as a valuable resource with which to further explore how SUMOylation regulates protein function.

Plastids are essential for plant cells and serve as biochemical hubs during embryogenesis. Therefore, many knockout mutants of genes encoding plastid-targeted proteins are embryonic lethal in Arabidopsis. However, until now, the reason for such embryonic lethal phenotypes was thought to be related to a general lack of essential plastid-generated metabolites, such as lipids or amino acids. Much less was known about a potential specific role of plastids during embryogenesis. GENOMES UNCOUPLED 1 (GUN1) and DELAYED GREENING 1 (DG1) are plastid-localized proteins that are involved in RNA editing when bound to MULTIPLE ORGANELLAR RNA-EDITING FACTOR 2 (MORF2). However, at least for GUN1, an enigmatic role in retrograde signalling is known to affect nuclear gene expression in response to plastid signals.

The researchers identify a recessive dg1 mutant that leads to embryo arrest at the globular stage in a quarter of the progeny from heterozygous plants — presumably the homozygous embryos. Expression of WUS and STM, which is normally confined to the inter-cotyledonary zone, is expanded in these mutants, and vascular identity does not reach the cotyledon primordia. In wild-type embryos, DG1 is expressed broadly except in the incipient shoot apical meristem, in line with the idea that DG1 represses WUS and STM. This role of DG1 is independent of its interaction with MORF2 and consequently of plastid RNA editing, which depends on the MORF2 interaction. Instead, the defect in dg1 embryos is partially suppressed by the gun1 mutant, with double mutants progressing to the torpedo stage and showing normal expression of WUS and STM. These results suggest that expression of WUS and STM is influenced by a plastid retrograde signal, which contributes to embryo patterning.

The photosynthetic electron flux from photosystem I (PSI) is mainly directed to NADP⁺ and CO₂ fixation, but a fraction is always shared between alternative and cyclic electron transport. Although the electron transfer from P700 to ferredoxin, via phylloquinone and the FeS_X, FeS_B and FeS_A clusters, is well characterized, the regulatory role of these redox intermediates in the delivery of electrons from PSI to NADP⁺, alternative and cyclic electron transport under environmental stress remains elusive. Here we provide evidence for sequential damage to PSI FeS clusters under high light and subsequent slow recovery under low light in Arabidopsis thaliana. Wild-type plants showed 10–35% photodamage to their FeS_A/B clusters with increasing high-light duration, without much effect on P700 oxidation capacity, FeS_X function or CO₂ fixation rate, and without additional oxygen consumption (O₂ photoreduction). Parallel FeS_A/B cluster damage in the pgr5 mutant was more pronounced at 50–85%, probably due to weak photosynthetic control and low non-photochemical quenching. Such severe electron pressure on PSI was also shown to damage the FeS_X clusters, with a concomitant decrease in P700 oxidation capacity and a decrease in thylakoid-bound ferredoxin in the pgr5 mutant. The results from wild-type and pgr5 plants reveal controlled damage of PSI FeS clusters under high light. In wild-type plants, this favours electron transport to linear over alternative pathways by intact PSI centres, thereby preventing reactive oxygen species production and probably promoting harmless charge recombination between P700⁺ and FeS_X⁻ as long as the majority of FeS_A/B clusters remain functional.

The cause of asymmetrical organ growth is differential distribution of a biochemical signal, such as a small RNA, protein or hormone. A recent study led by Hong Lilan from Zhejiang University uses the Arabidopsis sepal as a small and robust model of morphogenesis to understand what keeps it mostly flat during late flower development. The researchers isolated mutants with curved sepals bending outwards. The causal gene is VIP4, which encodes a component of the transcriptional regulator PAF1C. Its mutation causes an imbalance in growth rates and mechanical properties between abaxial and adaxial sides. A transcriptome analysis points to ARF3 and ARF4, two genes that are involved in auxin signalling and upregulated in the mutant, as potential downstream candidates, and a genetic approach confirmed this.

More experiments, including direct visualization of an ARF3–GFP (green fluorescent protein) construct, showed that transient and asymmetric distribution of ARF3, controlled directly by VIP4 (and indirectly via small mobile RNAs), is necessary for the sepal to stay flat. ARF3, in turn, affects auxin transport and signalling and cell wall stiffness through the expression of pectin methylesterases such as VGD1. So, quite counter-intuitively, in the wild-type sepal asymmetric ARF3 expression is needed for both sides to reach equivalent growth and stiffness. From an initial imbalance comes the symmetry that allows the sepal to grow flat.

RNA secondary structure (RSS) of primary microRNAs (pri-miRNAs) is a key determinant for miRNA production. Here we report that RNA helicase (RH) Brr2a, best known as a spliceosome component, modulates the structural complexity of pri-miRNAs to fine tune miRNA yield. Brr2a interacts with microprocessor component HYL1 and its loss reduces the levels of miRNAs derived from both intron-containing and intron-lacking pri-miRNAs. Brr2a binds to pri-miRNAs in vivo and in vitro. Furthermore, Brr2a hydrolyses ATP and the activity can be significantly enhanced by pri-miRNAs. Consequently, Brr2a unwinds pri-miRNAs in vitro. Moreover, Brr2a variants with compromised ATPase or RH activity are incapable of unwinding pri-miRNA, and their transgenic plants fail to restore miRNA levels in brr2a-2. Importantly, most of tested pri-miRNAs display distinct RSS, rendering them unsuitable for efficient processing in brr2a mutants vs Col-0. Collectively, this study reveals that Brr2a plays a non-canonical role in miRNA production beyond splicing regulation.

Tree species diversity is essential to sustaining stable forest ecosystem functioning. However, it remains unclear how boreal tree species diversity has changed in response to climate change and how it is associated with productivity and the temporal stability of boreal forest ecosystems. By combining 5,312 field observations and 55,560 Landsat images, here we develop a framework to estimate boreal tree species diversity (represented by the Shannon diversity index, H′) for the years 2000, 2010 and 2020. We document an average increase in H′ by 12% from 2000 to 2020 across the boreal forests. This increase accounts for 53% of all boreal forest areas and mainly occurs in the eastern forest–boreal transition region, the Okhotsk–Manchurian taiga and the Scandinavian–Russian taiga. Tree species diversity responds positively to increasing temperatures, but the relationship is weakened for higher temperature changes, and in areas of extreme warming (>0.065 °C yr⁻¹), a negative impact on tree species diversity is found. We further show that the observed spatiotemporal increase in diversity is significantly associated with increased productivity and temporal stability of boreal forest biomass. Our results highlight climate-warming-driven increases in boreal tree species diversity that positively affect boreal ecosystem functioning but are countered in areas of extreme warming.

Led by Yoann Le Bagousse-Pinguet of Avignon University, an international team of researchers undertook global field surveys of drylands, gathering data on plant morphology, traits and the chemical composition of the 301 plant species encountered. A compilation of more than 130,000 trait measurements revealed that once an aridity threshold has been passed, plant trait diversity in fact doubles.

This threshold represents the transition from semi-arid to arid conditions, and previous studies have shown that once this threshold has been passed, abrupt changes occur, including declines in soil fertility, plant productivity, cover and species richness. The surprising increase in plant functional diversity uncovered in this study was found to be coupled with declines in plant cover, leading the authors of this study to hypothesize that the increase in plant trait diversity was driven by a breakdown in plant–plant interactions that allows unique species to escape competition. This idea was supported by the finding that increases in grazing pressure, a major driver of decreasing plant cover, expand the plant trait space and modulate the aridity threshold at which trait diversity increased.