Plant, Cell & Environment最新文献

Plant growth and development are governed via signal networks that connect inputs from nutrient status, hormone signals, and environmental cues. Substantial researches have indicated a pivotal role of sugars as signalling molecules in plants that integrate external environmental cues and other nutrients with intrinsic developmental programmes regulated via multiple plant hormones. Therefore, plant growth and development are controlled through complication signalling networks. However, in many studies, to obtain more obviously experimental findings, excess concentrations of applied exogenous sugars have aggravated the complexity of this signalling networks. Once researchers underestimate this complexity, a series of contradictory or contrasting findings will be generated. More importantly, in terms of these contradictory findings, more contradictory study outcomings are derived. In this review, we carefully analyze some reports, and find that these reports have confused or neglected that the sugar-antagonism of ethylene signalling is specific or conditional. As a result, many contradictory conclusions are generated, which will in turn misdirect the scientific community.

Plants produce an immense diversity of defensive specialized metabolites. However, despite extensive functional characterization, the relative importance of different defensive compounds is rarely examined in natural settings. Here, we compare the efficacy of three Nicotiana benthamiana defensive compounds, nicotine, acylsugars and a serine protease inhibitor, by growing plants with combinations of knockout mutations in a natural setting, quantifying invertebrate interactions and comparing relative plant performance. Among the three tested compounds, acylsugars had the greatest defensive capacity, affecting aphids, leafhoppers, spiders and flies. Nicotine mutants displayed increased leafhopper feeding and aphid colonization. Plants lacking both nicotine and acylsugars were more susceptible to flea beetles and thrips. By contrast, knockout of the serine protease inhibitor did not affect insect herbivory in the field. Complementary experiments under controlled laboratory conditions with caterpillars, grasshoppers and aphids confirmed results obtained in a natural setting. We conclude that the three metabolite groups collectively provide broad-spectrum protection to N. benthamiana. However, there is a gradient in their effects on the interacting invertebrates present in the field. Furthermore, we demonstrate that, even if individual metabolites do not have a measurable defensive benefit on their own, they can have an additive effect when combined with other defensive compounds.

After an initial evolution in a reducing environment, life got successively challenged by reactive oxygen species (ROS), especially during the great oxidation event (GOE) that followed the development of photosynthesis. Therefore, ROS are deeply intertwined into the physiological, morphological and transcriptional responses of most present-day organisms. Copper-zinc superoxide dismutases (CuZnSODs) evolved during the GOE and are present in charophytes and extant land plants, but nearly absent from chlorophytes. The chemical inhibitor of CuZnSOD, lung cancer screen 1 (LCS-1), could greatly facilitate the study of SODs in diverse plants. Here, we determined the impact of chemical inhibition of plant CuZnSOD activity, on plant growth, transcription and metabolism. We followed a comparative approach by using different plant species, including Marchantia Polymorpha and Physcomitrium patens, representing bryophytes, the sister lineage to vascular plants, and Arabidopsis thaliana. We show that LCS-1 causes oxidative stress in plants and that the inhibition of CuZnSODs provoked a similar core response that mainly impacted glutathione homoeostasis in all plant species analysed. That said, Physcomitrium and Arabidopsis, which contain multiple CuZnSOD isoforms showed a more complex and exacerbated response. In addition, an untargeted metabolomics approach revealed a specific metabolic signature for each plant species. Our comparative analysis exposes a conserved core response at the physiological and transcriptional level towards LCS-1, while the metabolic response largely varies. These differences correlate with the number and localization of the CuZnSOD isoforms present in each species.

In ecophysiology leaves are frequently stored for hours after sampling before measuring their leaf water potential (Ψ_leaf). Here, we address a previously unidentified source of error, that metabolic heat generation can cause continuous water loss from leaves stored in impermeable bags, leading to a Ψ_leaf drop over time. We tested Ψ_leaf drop rates under various conditions: two bag materials, two species, initial Ψ_leaf above or below the turgor loss point (Ψ_tlp), and storage at 25°C versus 4°C. We partitioned leaf water loss due to condensation on the inner bag surface or permeation through the bag. We found that Ψ_leaf dropped by up to 0.39 MPa per hour, with 41%-89% of the water leaving the leaf condensed on the inner bag surface. Plastic bags showed higher Ψ_leaf drop rates than aluminium bags, and leaves above Ψ_tlp experienced greater drops. Storing leaves at 4°C reduced the Ψ_leaf drop rate by 60% compared to 25°C. Leaves were 0.2-0.3°C warmer than the bags, likely due to metabolic heating. Our energy balance model suggests that water loss is lower when storing leaves at cooler temperatures, using leaves with low stomatal conductance, deflated bags, and leaves with low Ψ_leaf.

Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) has decimated kiwifruit orchards growing susceptible kiwifruit Actinidia chinensis varieties. Effector loss has occurred recently in Psa3 isolates from resistant kiwifruit germplasm, resulting in strains capable of partially overcoming resistance present in kiwiberry vines (Actinidia arguta, Actinidia polygama, and Actinidia melanandra). Diploid male A. melanandra recognises several effectors, sharing recognition of at least one avirulence effector (HopAW1a) with previously studied tetraploid kiwiberry vines. Sequencing and assembly of the A. melanandra genome enabled the characterisation of the transcriptomic response of this non-host to wild-type and genetic mutants of Psa3. A. melanandra appears to mount a classic effector-triggered immunity (ETI) response to wildtype Psa3 V-13, as expected. Surprisingly, the type III secretion (T3SS) system-lacking Psa3 V-13 ∆hrcC strain did not appear to trigger pattern-triggered immunity (PTI) despite lacking the ability to deliver immunity-suppressing effectors. Contrasting the A. melanandra responses to an effectorless Psa3 V-13 ∆33E strain and to Psa3 V-13 ∆hrcC suggested that PTI triggered by Psa3 V-13 was based on the recognition of the T3SS itself. The characterisation of both ETI and PTI branches of innate immunity responses within A. melanandra further enables breeding for durable resistance in future kiwifruit cultivars.

The recent invasion of the fall armyworm (FAW) into Asia not only has had a major impact on maize yield but is feared to also pose a risk to rice production. We hypothesized that the brown planthopper (BPH) may aggravate this risk based on a recently discovered mutualism between the planthopper and the rice striped stem borer. Here we show that BPH may indeed facilitate a shift of FAW to rice. FAW females were found to strongly prefer to oviposit on BPH-infested rice plants, which emitted significantly elevated levels of five volatile compounds. A synthetic mixture of these compounds had a potent stimulatory effect on ovipositing females. Although FAW caterpillars exhibited relatively poor growth on both uninfested and BPH-infested rice, a considerable portion completed their development on young plants. Moreover, FAW were found to readily pupate and survive in exceedingly moist soils typical for rice cultivation, further highlighting FAW's potential to switch to rice. We conclude that BPH, by changing the bouquet of volatiles emitted by rice plants, may greatly facilitate this switch. These findings, together with a current increase of nonflooded upland rice in Asia, warrant careful monitoring and specific control measures against FAW to safeguard Asian rice production.

Fusarium oxysporum, an important soilborne fungal pathogen that causes serious Fusarium wilt disease, secretes diverse effectors during the infection. In this study, we identified a novel secreted cysteine-rich protein, FolSCP1, which contains unknown protein functional domain. Here, we characterized FolSCP1 as a secreted virulence factor that promotes the pathogen infection of host plants by inhibiting diverse plant defence responses. FolSCP1 interacted with the pathogenesis-related 5 (PR-5) protein SlPR5, a positive regulator of tomato plant immunity against multiple tomato pathogens, and effectively attenuated the antifungal activity of the tomato PR-5 protein. FoSCP1, a homologue of FolSCP1, was secreted by a F. oxysporum isolate from infected tobacco and targeted the tobacco PR-5 protein NtPR5 to suppress plant defence for further infection. In summary, our study revealed a fungal virulence strategy in which F. oxysporum secrete effectors that interfere with plant immunity by binding to the PR-5 protein of the host plant and inhibiting its biological activity, thereby promoting fungal infection.

Breeding tree genotypes that are both productive and drought-resistant is a primary goal in forestry. However, the relationships between plant hydraulics and yield at the genotype level, and their temporal stabilities, remain unclear. We selected six poplar genotypes from I-101 (Populus alba) × 84 K (P. alba × Popolus tremula var. glandulosa) for experiments in the first and fourth years after planting in a common garden. Measurements included stem embolism resistance, shoot hydraulic resistance and its partitioning between stems and leaves, vessel- and pit-level anatomy, leaf carbon acquisition capacity, carbon allocation to leaves, and aboveground biomass (yield proxy). Significant genetic variations in hydraulic properties and yield were found among genotypes in both years. Productive genotypes had wide vessels, large thin pit membranes, small pit apertures, and shallow pit chambers. Hydraulic resistance was negatively correlated with yield, enabling high stomatal conductance and assimilation rates. Productive genotypes allocated less aboveground carbon and hydraulic resistance to leaves. Temporally stable trade-offs between stem embolism resistance and yield, and between hydraulic segmentation and yield, were identified. These findings highlight the tight link between hydraulic function and yield and suggest that stable trade-offs may challenge breeding poplar genotypes that are both productive and drought-resistant.

Pandemics originating from zoonotic viruses have posed significant threats to human health and agriculture. Recent discoveries have revealed that wild-rice plants also harbour viral pathogens capable of severely impacting rice production, a cornerstone food crop. In this study, we conducted virome analysis on ~1000 wild-rice individual colonies and discovered a novel single-strand positive-sense RNA virus prevalent in these plants. Through comprehensive genomic characterization and comparative sequence analysis, this virus was classified as a new species in the genus Polerovirus, designated Rice less tiller virus (RLTV). Our investigations elucidated that RLTV could be transmitted from wild rice to cultivated rice via a specific insect vector, the aphid Rhopalosiphum padi, causing less tiller disease symptoms in rice plants. We generated an infectious cDNA clone for RLTV and demonstrated systemic infection of rice cultivars and induction of severe disease symptoms following mechanical inoculation or stable genetic transformation. We further illustrated transmission of RLTV from stable transgenic lines to healthy rice plants by the aphid vector, leading to the development of disease symptoms. Notably, our database searches showed that RLTV and another polerovirus isolated from a wild plant species are widely circulating not only in wild rice but also cultivated rice around the world. Our findings provide strong evidence for a wild plant origin for rice viruses and underscore the imminent threat posed by aphid-transmitted rice Polerovirus to rice cultivar.

In the semi-arid grasslands of the southwest United States, annual precipitation is divided between warm-season (July-September) convective precipitation and cool-season (December-March) frontal storms. While evidence suggests shifts in precipitation seasonal distribution, there is a poor understanding of the ecosystem carbon flux responses to cool-season precipitation and the potential legacy effects on subsequent warm-season carbon fluxes. Results from a two-year experiment with three cool-season precipitation treatments (dry, received 5th percentile cool-season total precipitation; normal, 50th; wet, 95th) and constant warm-season precipitation illustrate the direct and legacy effects on carbon fluxes, but in opposing ways. In wet cool-season plots, gross primary productivity (GPP) and ecosystem respiration (ER) were 103% and 127% higher than in normal cool-season plots. In dry cool-season plots, GPP and ER were 47% and 85% lower compared to normal cool-season plots. Unexpectedly, we found a positive legacy effect of the dry cool-season treatment on warm-season carbon flux, resulting in a significant increase in both GPP and ER in the subsequent warm season, compared to normal cool-season plots. Our results reveal positive legacy effects of cool-season drought on warm-season carbon fluxes and highlight the importance of the relatively under-studied cool-growing season and its direct/indirect impact on the ecosystem carbon budget.