New Phytologist最新文献

Although nitrogen (N) enrichment and precipitation changes are known to influence plant phenology and reproduction via altered soil nutrient and water availability, as well as above- and belowground biological processes, how these phenological changes affect reproduction remains unclear. Based on a field experiment with N addition and altered precipitation conducted in an alpine meadow on the eastern Tibetan Plateau since 2020, we explored their effects on plant reproductive phenology, reproductive output, and success from 2023 to 2024. N addition delayed the reproductive period, reduced the flowering asynchrony, and decreased both flower and fruit production in alpine plants. Notably, the interactive effects of N and precipitation addition significantly enhanced fruit set. Phenological shifts mediated plant reproductive responses to N addition and altered precipitation. Specifically, while N addition directly decreased flower and fruit production, it indirectly enhanced fruit set via phenological changes (including the peak flowering and the start of fruiting). These findings highlight the critical role of phenology in mediating alpine plant reproduction responses to N enrichment. Although delayed reproductive phenology enhances fruit set in alpine plants, its compensatory effect on N-induced reproductive losses remains limited under continuous nitrogen enrichment.

Postharvest pathogens can infect fresh produce both before and after harvest, by direct or wound-enhanced penetration, remaining quiescent until ripening. Biotrophic-like postharvest pathogens persist beneath host cells and can remain in a state of quiescence. They detect environmental cues and regulate quiescence through chromatin-level control and the secretion of effectors that interact with host pattern recognition receptors. By contrast, necrotrophic fungi persist between dead cells and depend more directly on nutrient availability to prime their growth and upon secretion for fungal virulence factors. During quiescence, the host also mounts specific responses, including activation of pattern recognition receptor genes, ethylene signaling (particularly in unripe fruit), and defense genes such as PR-10 and chitinases. Jasmonic acid and ethylene pathways synergistically enhance these defenses. As fruit ripens, the transition from quiescence to active necrotrophic growth is triggered, accelerating tissue decay. This activation is driven by several key factors, including weakened host defenses, decreased levels of antifungal compounds such as polyphenols, increased cell wall accessibility due to fruit softening and ripening-associated changes in signaling pathways, which alter environmental pH, carbon metabolism, and secondary metabolite production. These regulatory mechanisms collectively govern the timing and extent of fungal initiation of colonization during fruit senescence.

Argonaute2 (AGO2) largely participates in maintaining viral defenses. However, its function is not understood in species that are not commonly challenged by viruses in their native habitats. The ecological model species, Nicotiana attenuata, grows in arid/desert habitats. Natural virus infections are not commonly observed in this species even when the genes essential for viral defenses, like the RdRs, are silenced. The biological function of NaAGO2 has remained elusive. Silencing NaAGO2 with inverted-repeats (irAGO2) did not alter morphology, growth, or reproductive performance of unstressed plants compared to the wild-type (WT). irAGO2 was also able to defend against herbivores or pathogens and compete with con-species neighbors. However, irAGO2 had increased tolerance to water stress, exhibiting enhanced reproductive output during drought and recovery. Water-stressed irAGO2 accumulated significantly more abscisic acid (ABA) and proline, which are critical signaling and protective metabolites. Drought-responsive miRNA accumulation patterns were largely altered in irAGO2, potentially modulating ABA and proline gene expression during water stress and recovery. The function of three such Na-miRNAs (miR156, miR172, and miR398) was examined by transient overexpression in mitigating water stress and regulating ABA and proline pathways. We infer that AGO2 functions in fine-tuning ABA and proline homeostasis that optimizes N. attenuata's growth in complex stressful environments.

Seed dispersal modes play a crucial role in angiosperm migration, adaptation, and responses to climate change, yet their global spatiotemporal patterns and underlying drivers remain largely unexplored. Here, using a global dataset on seed dispersal modes (zoochory, anemochory, hydrochory, and autochory) of 35 131 angiosperm species, we provide a large-scale assessment of their evolutionary dynamics, diversification impact, and geographic variation. We found that the increase in zoochorous lineages began after c. 105 Ma, and the transition rate from abiotic-to-biotic dispersal strongly correlated with paleotemperature, being positive from 105 to 90 Ma and negative thereafter. However, contrary to previous hypotheses, we found no significant effect of seed dispersal mode on diversification rates across angiosperms. Spatially, the prevalence of zoochory declined, and that of autochory increased with latitude, both closely linked to contemporary temperature. Meanwhile, the frequency of zoochory and anemochory was positively associated with temperature anomalies since the Last Glacial Maximum, suggesting that dispersal modes facilitating long-distance dispersal are favored in climatically unstable regions. These findings highlight the key role of climate fluctuations in shaping the spatiotemporal patterns of angiosperm seed dispersal modes and suggest a more complex relationship between dispersal modes and angiosperm diversification than previously assumed.

The sapwood area supporting a given leaf area (Huber value, v_H) reflects the coupling between carbon uptake and water transport and loss at a whole-plant level. Geographic variation in v_H presumably reflects plant strategic adaptations, but the lack of a general explanation for such variation hinders its representation in vegetation models and assessment of its impact on the global carbon and water cycles. Here we develop a simple hydraulic trait model to predict optimal v_H by matching stem water supply and leaf water loss, and test its performance against two extensive plant hydraulic datasets. We show that our eco-evolutionary optimality-based model explains nearly 60% of global v_H variation in response to light, vapour pressure deficit, temperature and sapwood conductivity. Enhanced hydraulic efficiency with warmer temperatures reduces the sapwood area required to support a given leaf area, whereas high irradiance (supporting increased photosynthetic capacity) and drier air increase it. This study thus provides a route to modelling variation in functional traits through the coordination of carbon uptake and water transport processes.

The Grant-Stebbins model predicts that a plant species encountering different pollinators across its range may undergo local adaptation and, subsequently, ecological speciation. We tested whether this could explain the origin of Aeschynanthus acuminatus (Gesneriaceae), a species phylogenetically derived from sunbird specialist ancestors. A. acuminatus is widespread throughout mainland E Asia but also occurs in Taiwan, beyond the range of sunbirds, where it is pollinated by generalist passerines. We hypothesized that A. acuminatus originated from an ancestral lineage that colonized Taiwan, rapidly adapted to its novel pollinator fauna, and secondarily spread to the mainland. We tested among evolutionary scenarios by integrating studies of phylogeography, pollination, and floral morphology. Phylogeographic analysis of genome-wide SNPs revealed a mainland origin. Pollinator observations showed varied visitation by both sunbirds and generalist passerines across mainland Asia. The origin of A. acuminatus likely involved a pollinator niche expansion to include generalist passerines, an ecological shift that enabled its subsequent range expansion. Hypothetical pollinator-mediated fitness models suggest that the derived floral morphology of A. acuminatus represents an adaptive optimum for generalist passerine pollination rather than an intermediate phenotype. Our research illustrates how the evolution of pollinator niches can influence the origin and range dynamics of plant species.

Tree rings are considered the gold standard for observing variation in past atmospheric radiocarbon (¹⁴C), yet little attention has been paid to whether different trees record tropospheric ¹⁴C evenly. The discovery of Miyake events, rapid increases in ¹⁴C production occurring in past millennia, has led to repeated measurements of ¹⁴C in tree rings across species and locations. These records demonstrate remarkable synchrony, yet significant variability between samples remains, limiting reliable use of tree rings as a precise indicator of the timing and scale of past ¹⁴C production. Understanding how trees and species record tropospheric ¹⁴C would improve reconstructions of past ¹⁴C production events, refine geochronological control, and because of the pulse-like nature of past ¹⁴C production events, shed light on a fundamental question in tree physiology and dendrochronology: what is the lag time between photosynthesis, storage, and allocation to wood and how might this lag blur isotopic signals in tree rings? Here, we evaluate the implicit assumption that all trees record tropospheric ¹⁴C evenly by focusing on the path carbon takes within trees including: phenology of carbon uptake and wood formation, storage and use of nonstructural carbohydrates, and how these factors interact to affect the tropospheric ¹⁴C signal in wood.

Cassava (Manihot esculenta) is a staple crop across the global south, yet modern varieties may have limited genetic diversity due to historical bottlenecks. We investigated the genomic diversity of over 1000 cassava genotypes, incorporating 387 newly sequenced Colombian landraces originating from diverse climates. We hypothesized that landraces retain untapped variation useful for breeding and adaptation. Whole-genome sequencing was used to characterize landraces and breeding lines. We assessed genetic differentiation across geography and climate and analyzed the distribution of loss-of-function (LoF) mutations to identify potential targets for gene editing. Landraces maintained high and novel dimensions of genetic diversity compared to breeding lines from Asia and Africa. Differentiation among landraces reflected both demography and climate of origin. LoF analyses indicated purging of deleterious alleles through inbreeding, but LoF alleles were retained in genes enriched for coumarin biosynthesis and plant immunity, suggesting selection for postharvest quality and disease resistance. Climate-associated loci were explored for their adaptive potential. Cassava landraces represent a critical reservoir of genetic diversity. This study establishes a foundation for leveraging landrace variation to accelerate cassava improvement through gene editing and targeted breeding.

Oula Ghannoum, Western Sydney University's Hawkesbury Institute for the Environment (Australia).