New Phytologist最新文献

• Cuticular wax is essential for fruit to maintain moisture. Although the wax content of peel surface in apple (Malus spp.) varies, the detailed molecular mechanism remains unclear.
• Here, we identified the β-ketoacyl-CoA synthase 2 (MdKCS2) differentially expressed between apple peel with low and high wax content by integrating bulked segregant analysis-sequencing and RNA-seq. We found that a 63-bp insertion in the MdKCS2 promoter was the primary reason for apple peel with low wax content. The 63-bp insertion reduced MdKCS2 promoter activity and enhanced the DNA binding with the suppressor MdDOF4.6, decreasing wax biosynthesis by reducing C24 very-long-chain fatty acid (VLCFA).
• ECERIFERUM 2 (MdCER2) was co-expressed with MdKCS2 and suppressed by MdMYB56, MdbHLH137 and MdDOF4.6, further decreasing C29 alkane content in apple peel with low C24 VLCFA content.
• Overall, MdKCS2 and MdCER2 are coordinately involved in the wax production of apple peel surface.

• Powdery mildew is an economically important disease caused by c. 1000 different fungal species. Erysiphe vaccinii is an emerging powdery mildew species that is impacting the blueberry industry. Once confined to North America, E. vaccinii is now spreading rapidly across major blueberry-growing regions, including China, Morocco, Mexico, and the USA, threatening millions in losses.
• This study documents its recent global spread by analyzing both herbarium specimens, some over 150-yr-old, and fresh samples collected world-wide.
• Our findings were integrated into a ‘living phylogeny’ via T-BAS to simplify pathogen identification and enable rapid responses to new outbreaks. We identified 50 haplotypes, two primary introductions world-wide, and revealed a shift from a generalist to a specialist pathogen.
• This research provides insights into the complexities of host specialization and highlights the need to address this emerging global threat to blueberry production.

• Specialized metabolites are molecules involved in plants' interaction with their environment. Elucidating their biosynthetic pathways is a challenging but rewarding task, leading to societal applications and ecological insights. Furanocoumarins emerged multiple times in Angiosperms, raising the question of how different enzymes evolved into catalyzing identical reactions.
• To identify enzymes producing lineage-specific metabolites, an evolutionary-based approach was developed and applied to furanocoumarin biosynthesis in Ficus carica (Moraceae). This led to the characterization of CYP71B129–131a, three P450 enzymes whose evolution of the function was investigated using phylogenetics, structural comparisons and site-directed mutagenesis.
• CYP71B129 and CYP71B130,131a were found to hydroxylate umbelliferone (coumarin) and xanthotoxin (furanocoumarin), respectively. Results suggest that CYP71Bs xanthotoxin hydroxylase activity results from duplications and functional divergence of umbelliferone hydroxylase genes. Structural comparisons highlighted an amino acid affecting CYP71Bs substrate specificity, which may play a key role in allowing xanthotoxin hydroxylation in several P450 subfamilies.
• CYP71B130-131a characterization validates the proposed enzyme-discovery approach, which can be applied to different pathways and help to avoid the classic bottlenecks of specialized metabolism elucidation. The CYP71Bs also exemplify how furanocoumarin-biosynthetic enzymes can stem from coumarin-biosynthetic ones and provides insights into the molecular mechanisms underlying the multiple emergences of xanthotoxin hydroxylation in distant P450 subfamilies.

• The effects of drought stress on stomatal opening dynamics, plant volatile organic compound (VOC) emissions and plant–insect interactions have been well-documented individually, but how they interact mechanistically remains poorly studied.
• Here, we studied how drought-triggered stomatal closure affects VOC emission and plant–trophic interactions by combining RNAi silencing, molecular biological and chemical analyses (GC-MS) of a potato-tuber moth-egg parasitoid tritrophic system.
• Drought stress attenuated stomatal apertures and VOC emissions, which made the potato (Solanum tuberosum L.) plants more attractive to the herbivore but less attractive to the parasitoid. Stomatal aperture manipulations through StSLAC1 gene knockdown and chemical treatments (ABA and 5-aminolevulinic acid) consistently affected drought-triggered VOC emissions and plant–herbivore–parasitoid interactions, supporting aperture-dependent VOC emission. RNA-Seq analysis revealed that drought stress did not transcriptionally inhibit VOC biosynthesis.
• Collectively, our findings are consistent with the stomatal regulation of plant–insect interactions through the modulation of VOC emissions under drought stress. This highlights the intricate interplay between stomatal dynamics, VOC emission and plant–insect interactions.

• Plant survival in a warmer world requires the timely adjustment of biological processes to cyclical changes in the new environment. Circadian oscillators have been proposed to contribute to thermal adaptation and plasticity. However, the influence of temperature on circadian clock performance and its impact on plant behaviour in natural ecosystems are not well-understood.
• We combined bioinformatics, molecular biology and ecophysiology to investigate the effects of increasing temperatures on the functioning of the circadian clock in two closely related tree species from Patagonian forests that constitute examples of adaptation to different thermal environments based on their altitudinal profiles.
• Nothofagus pumilio, the species from colder environments, showed a major rearrangement of its transcriptome and reduced ability to maintain rhythmicity at high temperatures compared with Nothofagus obliqua, which inhabits warmer zones. In altitude-swap experiments, N. pumilio, but not N. obliqua, showed limited oscillator function in warmer zones of the forest, and reduced survival and growth.
• Our findings show that interspecific differences in the influence of temperature on circadian clock performance are associated with preferred thermal niches, and to thermal plasticity of seedlings in natural environments, highlighting the potential role of a resonating oscillator in ecological adaptation to a warming environment.

• Stress often induces plant trait plasticity, and microbial communities also alter plant traits. Therefore, it is unclear how much plasticity results from direct plant responses to stress vs indirect responses due to stress-induced changes in soil microbial communities.
• To test how microbes and microbial community responses to stress affect the ecology and potentially the evolution of plant plasticity, I grew plants in four stress environments (salt, herbicide, herbivory, and no stress) with microbes that had responded to these same environments or with sterile inoculant.
• Plants delayed flowering under stress only when inoculated with live microbial communities, and this plasticity was maladaptive. However, microbial communities responded to stress in ways that accelerated flowering across all environments. Microbes also affected the expression of genetic variation for plant flowering time and specific leaf area, as well as genetic variation for plasticity of both traits, and disrupted a positive genetic correlation for plasticity in response to herbicide and herbivory stress, suggesting that microbes may affect the pace of plant evolution.
• Together, these results highlight an important role for soil microbes in plant plastic responses to stress and suggest that microbes may alter the evolution of plant plasticity.

• Furanocoumarins (FCs) are plant defence compounds derived from the phenylpropanoid pathway via the coumarin umbelliferone that harbour some therapeutic benefits yet are the underlying cause of ‘grapefruit–drug interactions’ in humans. Most of the pathway genes have not been identified in citrus.
• We employed a genetic/Omics approach on citrus ancestral species and F1 populations of mandarin × grapefruit and mandarin × pummelo. Enzyme specificity was characterized by In vivo 2-oxoglutarate-dependent dioxygenase family (2OGD) activity assays.
• We identified a 2OGD multi-gene cluster involved in coumarin/FC/pyranocoumarin biosynthesis; Species lacking FCs in leaves/fruit were homozygous for a 655-base solo-LTR frame-disrupting insertion within one dual specificity C2′H/F6′H encoding 2OGD gene, demonstrating that integrity of this gene is fully correlated with the capacity to biosynthesize metabolites of the extended FC pathway in leaves/fruit. A second 2OGD is the prominent gene expressed in citrus roots, which contain a unique pattern of extended FC pathway metabolites, including the predominant pyranocoumarins. A third 2OGD gene encodes a single activity F6′H, which appears to be induced at the transcript level by citrus pathogens.
• The results provide insights into the genetic basis underlying the difference between citrus fruit FC producers (grapefruit and pummelo) and nonproducers (mandarin and orange) and provide a gene target to breed for FC-free varieties by marker-assisted breeding or genome editing.

Introduction and context

The role of cell wall composition in photosynthesis has only recently been proposed. Apparently contradictory results have been reported, but previous studies were often limited to single or closely related species. The aim of the present letter is to combine published and novel data on cell wall composition and photosynthesis limitations, including data for all the major land plant's phylogenetic groups (Supporting Information Methods S1; Dataset S1), to provide novel evidence on the importance of cell wall composition in determining mesophyll conductance to CO₂ diffusion (g_m) across land plants' phylogeny. We address the hypothesis that the pectin fraction of total major cell wall compounds is positively related to g_m and, consequently, to photosynthesis, when pooling species from across the entire phylogeny.