Molecular Horticulture最新文献

CRISPR-based gene editing has rarely been studied in plant pathogens. In this report, the CRISPR/FnCas12a system was successfully established for gene editing in Pseudomonas syringae pv. actinidiae (Psa), which causes bacterial canker (BC) of kiwifruit. The system was constructed in a Psa-suitable vector pBBR1-MCS2 to edit hopH1 or/and hopZ5, which encode effectors only present in Psa biovar 3 (Psa3) responsible for BC pandemic in kiwifruit worldwide. Two different CRISPR RNAs (crRNA) were designed to edit either hopH1 or/and hopZ5, and two different sets of PCR primers were used to screen deletions of the target genes and the presence of the vector in Psa. The deletion in Psa was impacted by the position of the DNAs targeted by the crRNAs. The vector-eliminated mutant could receive the editing system iteratively. Interestingly, the double mutant ΔhopZ5ΔhopH1 showed significantly stronger virulence than the wild-type Psa on Actinidia eriantha cv. White (resistant to BC), but weak virulence on A. chinensis cv. Hongyang (highly susceptible to BC), respectively, suggesting that hopH1 or/and hopZ5 potentially matches an unknown resistance gene in White. In summary, we have established the CRISPR/FnCas12a genome-editing system to probe gene function in the pathogen and to explore effector-target interactions in kiwifruit-Psa-pathosyetem.

Malate metabolism bridges plant evolutionary adaptation and fruit quality regulation, serving dual roles in energy metabolism (tricarboxylic acid cycle/glycolysis) and environmental stress responses (stomatal control, pH balance). In horticulture, apple malate content dictates flavor profiles, driving divergent consumer preferences (high-sugar in Asia vs. tartness in the West), necessitating precision breeding targeting vacuolar accumulation mechanisms. Recent bioinformatic studies and transporter biology (e.g., Ma1, ALMT) have revealed genetic regulators of malate homeostasis, yet transcriptional regulation and post-translational modifications (PTMs) of transporters remain poorly understood. Notably, cultivated varieties exhibit distinct malate-related traits compared to their wild relatives, a divergence attributable to artificial selection during domestication. Additionally, agroecological factors including light, temperature, and soil conditions, dynamically regulate malate biosynthesis and storage. This metabolic plasticity reflects evolutionary adaptations influenced by domestication. This review integrates molecular physiology and domestication genetics to dissect cross-scale regulation of malate networks. We propose a transporter-engineering framework for developing market-tailored varieties and highlight unresolved questions, including PTM-mediated transporter regulation and metabolic plasticity modeling for climate-resilient crops. Bridging evolutionary adaptation with quality-driven breeding targeting malate, this synthesis advances strategies for sustainable horticulture in shifting agroclimatic landscapes.

Citrate is critical to the flavor of horticultural fruit and governed by ACO. However, the specific ACO and its upstream regulators involved in citrate metabolism during pear (Pyrus spp.) fruit development remained uncharacterized. This study identified and characterized six PbrACOs from the Pyrus bretschneideri Rehd. genome. Comprehensive analyses of citrate levels, cyt/mitACO activities, and PbrACOs expression profiles in the pericarp and cortex tissues of developing 'Yali' and 'Dangshansuli' fruits revealed PbrACO2 as a candidate gene. Subsequently, PbrACO2 was confirmed as a mitochondrial aconitase catalyzing citrate-to-isocitrate conversion in vitro and in vivo. Analysis of differentially expressed transcription factors (TFs) and cis-acting elements in the PbrACO2 promoter identified nuclear PbrMYB3 and PbrMYB65, derived from whole genome duplication/segmental duplication, as candidate upstream regulators. These MYB TFs, without direct relationship, bound, as monomers, to the same two MYB-binding sites in the PbrACO2 promoter to activate its transcription, thereby promoting citrate isomerization in pear and tomato. Further investigation revealed that PbrMYB3 and PbrMYB65 are transcriptionally regulated by PbrNAC34a. Given their tissue-dependent expression profiles, the PbrNAC34a-PbrMYB3/65-PbrACO2 cascade partially accounts for citrate differences between pear fruit pericarp and cortex tissues. These findings enhance understanding of citrate accumulation in Rosaceae fruit and provide genetic resources for pear breeding.

Flavonols represent a large subgroup of flavonoids and function as the principal bioactive compounds in tea and medicinal chrysanthemum (Chrysanthemum morifolium) flowers. Low temperature is one of the most significant environmental factors influencing flavonol accumulation. Nevertheless, the regulatory mechanisms governing flavonol biosynthesis in response to low temperature remain predominantly uncharacterized. In this study, we observed decreased flavonol accumulation in chrysanthemum flowers under low-temperature conditions, correlating with reduced expression of the NAC transcription factor VND-INTERACTING2 (VNI2). The suppression of CmVNI2 resulted in diminished flavonol content. DNA affinity purification sequencing and RNA sequencing analyses demonstrated that CmVNI2 directly regulates the expression of CmF3H and CmMYB3, two genes essential for flavonol biosynthesis. In addition, transient overexpression of CmMYB3 in CmVNI2 RNA interference plants restored flavonol accumulation. The study establishes that the CmVNI2-CmMYB3 module plays a crucial role in regulating flavonol biosynthesis in chrysanthemum flowers under low-temperature stress and identifies potential target genes for enhancing the bioactive properties of chrysanthemum as a tea or medicinal herb.

Floral fragrance is essential for the attraction of pollinators and responses to biotic and abiotic stresses. It also enhances the quality and economic value of plants. Phytohormones, acting as key signaling molecules, are crucial roles in regulating plant growth and development. However, the molecular mechanisms underlying the biosynthesis of fragrance-related volatiles and their crosstalk with other endogenous signals within plants remain largely unknown. Here, we identified a sesquiterpene synthase gene, CmEβFS, in chrysanthemum, which encodes a catalytic enzyme responsible for synthesizing the key fragrance-related compound (E)-β-farnesene. We demonstrated that CmEβFS is negatively regulated by CmWRKY1, thereby inhibiting (E)-β-farnesene biosynthesis. Furthermore, CmWRKY1 interacts with the salicylic acid (SA) receptor CmNPR3 to regulate SA-mediated CmEβFS transcription. Our findings reveal that SA regulates (E)-β-farnesene biosynthesis by controlling CmEβFS expression via the CmWRKY1-CmNPR3 module during floral development. These findings enhanced our understanding of the mechanisms underlying SA-mediated regulation of volatile organic compounds (VOCs) biosynthesis and provided insights into improving floral fragrance.

Fruit domestication has long aimed to reduce bitterness, yet the molecular mechanisms behind this trait remain only partially understood. Wild apples and pears naturally accumulate high levels of bitter proanthocyanidins (PAs), also known as condensed tannins. In this study, a convergent domestication process was identified in both fruits, involving the selection of weak alleles of MYB transcription factors that regulate PA biosynthesis. In apples, domestication targeted the MYB-Tannin-Tamer (MdMYBTT) gene. A 411-base pair transposable element inserted into the third exon of this gene in cultivated varieties produced a truncated, non-functional protein unable to activate the PA biosynthetic gene Anthocyanidin Reductase 1 (ANR1). The resulting mdmybtt allele led to reduced PA levels and was fixed in domesticated apples through positive selection. Likewise, in pears, a 57-base pair insertion in the promoter of the MYBPA1 gene suppressed its expression in cultivated varieties, limiting PA production. This insertion created the mybpa1 allele, which was similarly fixed during pear domestication. These findings highlight a shared evolutionary strategy to reduce fruit bitterness by selecting mutations that suppress PA synthesis. These findings offer valuable insights into the molecular basis of domestication and inform breeding efforts to optimize both flavor and nutritional quality.

Nitrogen (N) is essential for the physiological metabolism, growth, and development of plants. Plants have evolved a complex regulatory network for the efficient regulation of N uptake and utilization to adapt to fluctuations in environmental N levels. However, the mechanisms underlying the regulation of N absorption and utilization in apple remain unclear. Here, we identified MdILR3 (IAA-LEUCINE RESISTANT3) as an upstream regulator of MdNRT2.4 through yeast one-hybrid (Y1H) screening. MdILR3 overexpression significantly up-regulated the expression of MdNRT2.3/2.4 and MdNIA1, resulting in an increase in nitrate content and nitrate reductase activity. Y1H and EMSA assays revealed that MdILR3 directly interacted with the promoters of MdNRT2.3/2.4 and MdNIA1. Furthermore, MdILR3 can directly bind to the promoter of MdSWEET12 and activate its expression, thereby regulating sucrose transport to provide energy for N uptake in roots. In summary, we provide physiological and molecular evidence suggesting that MdILR3 may positively regulate nitrate response by activating the expression of genes related to N uptake and sugar transport. Our findings suggest that genetic improvements in apple could enhance its ability to absorb and utilize N.

Seedless watermelons are increasingly dominating the consumer market due to their convenience and high quality. However, traditional triploid watermelon breeding faces challenges such as long breeding cycles and low survival rates of triploid F₁ progeny, severely hindering both breeding and production. In this study, we identified the ClPS1 gene as being associated with the formation of 2n gametes in watermelon. Expression analysis revealed that ClPS1 is highly expressed during meiosis and microsporogenesis. Using CRISPR/Cas9, we generated ClPS1-targeted mutants, which disrupted chromosome segregation at metaphase II. This led to the production of diploid male spores and abnormal division of male spores, ultimately generating diploid pollen grains, while female meiosis remained unaffected. Moreover, self-fertilization or crosses using these mutants as paternal parents yielded triploid and aneuploid watermelons. Our findings demonstrate, for the first time, the molecular manipulation of 2n gametes to create triploid seedless watermelons, offering new insights into polyploid breeding and evolutionary studies in the Cucurbitaceae family and other species.