New Phytologist最新文献

Cross-kingdom RNA interference (ckRNAi) is a mechanism of interspecies communication where small RNAs (sRNAs) are transported from one organism to another; these sRNAs silence target genes in trans by loading into host AGO proteins. In this work, we investigated the occurrence of ckRNAi in Arbuscular Mycorrhizal Symbiosis (AMS). We used an in silico prediction analysis to identify a sRNA (Rir2216) from the AM fungus Rhizophagus irregularis and its putative plant gene target, the Medicago truncatula MtWRKY69 transcription factor. Heterologous co-expression assays in Nicotiana benthamiana, 5' RACE reactions and AGO1-immunoprecipitation assays from mycorrhizal roots were used to characterize the Rir2216-MtWRKY69 interaction. We further analyzed MtWRKY69 expression profile and the contribution of constitutive and conditional MtWRKY69 expression to AMS. We show that Rir2216 is loaded into an AGO1 silencing complex from the host plant M. truncatula, leading to cleavage of a host target transcript encoding for the MtWRKY69 transcription factor. MtWRKY69 is specifically downregulated in arbusculated cells in mycorrhizal roots and increased levels of MtWRKY69 expression led to a reduced AM colonization level. Our results indicate that MtWRKY69 silencing, mediated by a fungal sRNA, is relevant for AMS; we thus present the first experimental evidence of fungus to plant ckRNAi in AMS.

Adaptive radiation in Ophrys orchids leads to complex floral phenotypes that vary in scent, color and shape. Using a novel pipeline to quantify these phenotypes, we investigated trait divergence at early stages of speciation in six populations of Ophrys aveyronensis experiencing recent allopatry. By integrating different genetic/genomic techniques, we investigated: variation and integration of floral components (scent, color and shape); phenotypes and genomic regions under divergent selection; and the genomic bases of trait variation. We identified a large genomic island of divergence, likely associated with phenotypic variation in particular in floral odor. We detected potential divergent selection on macular color, while stabilizing selection was suspected on floral morphology and for several volatile olfactive compounds. We also identified candidate genes involved in anthocyanin and in steroid biosynthesis pathways associated with standing genetic variation in color and odor. This study sheds light on early differentiation in Ophrys, revealing patterns that often become invisible over time, that is the geographic mosaic of traits under selection and the early appearance of strong genomic divergence. It also supports a crucial genomic region for future investigation and highlights the value of a multifaceted approach in unraveling speciation within taxa with large genomes.

We investigate the impact of a 20-yr irrigation on root water uptake (RWU) and drought stress release in a naturally dry Scots pine forest. We use a combination of electrical resistivity tomography to image RWU, drone flights to image the crown stress and sensors to monitor soil water content. Our findings suggest that increased water availability enhances root growth and resource use efficiency, potentially increasing trees' resistance to future drought conditions by enabling water uptake from deeper soil layers. This research highlights the significant role of ecological memory and legacy effects in determining tree responses to environmental changes.

Replicated trait evolution can provide insights into the mechanisms underlying the evolution of biodiversity. One example of replicated evolution is the awn, an organ elaboration in grass inflorescences. Awns are likely homologous to leaf blades. We hypothesized that awns have evolved repeatedly because a conserved leaf blade developmental program is continuously activated and suppressed over the course of evolution, leading to the repeated emergence and loss of awns. To evaluate predictions arising from our hypothesis, we used ancestral state estimations, comparative genetics, anatomy, and morphology to trace awn evolution. We discovered that awned lemmas that evolved independently share similarities in developmental trajectory. In addition, in two species with independently derived awns and differing awn morphologies (Brachypodium distachyon and Alopecurus myosuroides), we found that orthologs of the YABBY transcription factor gene DROOPING LEAF are required for awn initiation. Our analyses of awn development in Brachypodium distachyon, Alopecurus myosuroides, and Holcus lanatus also revealed that differences in the relative expansion of awned lemma compartments can explain diversity in awn morphology at maturity. Our results show that developmental conservation can underlie replicated evolution and can potentiate the evolution of morphological diversity.

Temperatures perceived early in the life cycle of mother plants can affect the germination of the offspring seeds. In Arabidopsis thaliana, vernalisation-insensitive mutants showed altered germination response to elevated maternal temperature, hence revealing a strong genetic determinism. However, the genetic control of this maternal effect and its prevalence across natural populations remain unclear. Here, we exposed a collection of European accessions of A. thaliana to increased temperature during the vegetative phase and assessed germination in their progeny to identify the genetic basis of transgenerational germination response. We found that genotypes with rapidly germinating progeny after early maternal exposure to elevated temperature originated from regions with low-light radiation. Combining genome-wide association, expression analysis and functional assays across multiple genetic backgrounds, we show a central role for PHYB in mediating the response to maternally perceived temperature at the vegetative stage. Differential gene expression analysis in leaves identified a similar genetic network as previously found in seed endosperm under elevated temperature, supporting the pleiotropic involvement of PHYB signalling across different tissues and stages. This provides evidence that complex environmental responses modulated by the maternal genotype can rely on a consistent set of genes yet produce different effects at the different stages of exposure.

The origin story of land plants - the pivotal evolutionary event that paved the way for terrestrial ecosystems of today to flourish - lies within their closest living relatives: the streptophyte algae. Streptophyte cell wall composition has evolved such that profiles of cell wall polysaccharides can be used as taxonomic markers. Since xyloglucan is restricted to the streptophyte lineage, we hypothesized that fungal enzymes evolved in response to xyloglucan availability in streptophyte algal or land plant cell walls. The record of the origins of these enzymes is embedded in fungal genomes, and comparing genomes of fungi that share an ancient common ancestor can provide insights into fungal interactions with early plants. This Viewpoint contributes a review of evidence underlying current assumptions about the distribution of xyloglucan in plant and algal cell walls. We evaluate evolutionary scenarios that may have given rise to the observed distribution of putative xyloglucanases in fungi and discuss possible biological contexts in which these enzymes could have evolved. Our findings suggest that fungal xyloglucanase evolution was more likely driven by land plant diversification and biomass accumulation than by the first origins of xyloglucan in streptophyte algal cell walls.

Numerous herbivore-induced plant volatiles (HIPVs) play important roles in plant defense. In tea plants (Camellia sinensis), (Z)-3-hexenyl acetate (3-HAC) has been characterized as associated with resistance to herbivores. To date, how tea plants biosynthesize and regulate 3-HAC to resist herbivores remain unclear. Based on transcriptomes assembled from Ectropis obliqua-fed leaves, a cDNA encoding BAHD acyltransferase, namely CsCHAT1, was highly induced in leaves fed with E. obliqua. Enzymatic assays showed that CsCHAT1 converted (Z)-3-hexenol into 3-HAC. Further suppression of CsCHAT1 expression reduced the accumulation of 3-HAC and lowered the resistance of tea plants to E. obliqua, while 3-HAC replenishment rescued the reduced resistance of CsCHAT1-silenced tea plants against E. obliqua. Two transcription factors (TFs), CsNAC30 and CsTCP11, were co-expressed with CsCHAT1. An integrative approach of biochemistry, DNA-protein interaction, gene silencing, and metabolic profiling revealed that the two TFs positively regulated the expression of CsCHAT1. The suppression of either one decreased the production of 3-HAC and eliminated the resistance of tea plants to E. obliqua. Notably, the suppression of either one considerably impaired JA-induced 3-HAC biosynthesis in tea plant. The proposed pathway can be targeted for innovative agro-biotechnologies protecting tea plants from damage by E. obliqua.

Long noncoding RNAs, including intergenic lncRNAs (lincRNAs), play a key role in various biological processes throughout the plant life cycle, and the advent of single-cell RNA sequencing (scRNA-seq) technology has opened up a valuable avenue for scrutinizing the intricate roles of lincRNAs in cellular processes. Here, we identified a new batch of lincRNAs using scRNA-seq data from diverse tissues of plants (rice, Arabidopsis, tomato, and maize). Based on well-annotated single-cell transcriptome atlases, plant lincRNAs were found to possess the same level of cell-type specificity as mRNAs and to be involved in the differentiation of certain cell types based on pseudo-time analysis. Many lincRNAs were predicted to play a hub role in the cell-type-specific co-expression networks of lincRNAs and mRNAs, suggesting their trans-acting abilities. Besides, plant lincRNAs were revealed to have potential cis-acting properties based on their genomic distances and expression correlations with the neighboring mRNAs. Furthermore, an online platform, PscLncRNA (http://ibi.zju.edu.cn/psclncrna/), was constructed for searching and visualizing all identified plant lincRNAs with annotated potential functions. Our work provides new insights into plant lincRNAs at single-cell resolution and an important resource for understanding and further investigation of plant lincRNAs.

Photoperiod is an environmental signal that varies predictably across the year. Therefore, the duration of sunlight available for photosynthesis and in turn the ability of plants to accumulate carbon resources also fluctuates across the year. To adapt to these variations in photoperiod, the metabolic daylength measurement (MDLM) system measures the photosynthetic period rather than the absolute photoperiod, translating it into seasonal gene expression changes linked to photoperiodic growth. In this Tansley Insight, we briefly summarize the current understanding of the MDLM system and highlight gaps in our knowledge. Given the system's critical role in seasonal growth, understanding the MDLM system is essential for enhancing plant adaptation to different photoperiods and optimizing agricultural production.

Direct human activity and global climatic changes are threatening the existence of many vegetated habitats. Seedling establishment, one of the riskiest plant life stages, must be successful for such habitats to persist. The establishment of seedlings is known to be enhanced by nurse effects, but most studies to date have looked at the nursing effects of plants while sidelining inanimate objects. Nevertheless, nurse objects can support seedling establishment via diverse mechanisms such as moderating abiotic stresses like extreme temperatures and drought, reducing negative biological interactions such as herbivory while enhancing positive processes like seed dispersal, and providing protection from physical disturbances such as trampling and fire. The robust nature of nurse objects highlights their potential in habitat restoration. The addition of nurse objects allows a simple, single-effort rehabilitation strategy that can later draw on natural seed dispersal and establishment. By achieving a better understanding of the processes in which nurse objects are involved we should be able to better predict vegetation dynamics and manipulate them to minimize adverse processes and support regeneration in natural habitats.