Horticultural Plant Journal最新文献

VIGS (Virus-induced gene silencing), a method for posttranscriptional gene silencing, is an effective technique for investigating the activities of genes in plants. Since there is no report for available VIGS system in Styrax japonicus, the application of a VIGS approach that results in a gene knockdown to study gene function is limited. In this study, we compared the characteristics that could affect the viability of VIGS in S. japonicus, including the acetosyringone (AS) concentration, the Agrobacterium's optical density and the inoculation method. The stable reference genes of S. japonicus were selected to validate the gene's knockdown by quantitative PCR. As a result, we successfully constructed 2 VIGS systems based on TRV virus: vacuum with AS concentration of 200 μmol·L⁻¹ and OD₆₀₀ of 0.5, and friction-osmosis with AS concentration of 200 μmol·L⁻¹ and OD₆₀₀ of 1.0, which silencing efficiency was 83.33% and 74.19%, respectively. The successfully applied VIGS method provides a rapid and effective reverse gene functional analysis approach in S. japonicus to identify unknown gene functions.

Jujube witches’ broom (JWB) caused by phytoplasma has a severely negative effect on multiple metabolisms in jujube. The GST gene family in plants participates in the regulation of a variety of biotic and abiotic stresses. This study aims to identify and reveal the changes in the jujube GST gene family in response to phytoplasma infection. Here, 70 ZjGSTs were identified in the jujube genome and divided into 8 classes. Among them, the Tau-class, including 44 genes, was the largest. Phylogenetic analysis indicated that Tau-class genes were highly conserved among species, such as Arabidopsis, cotton, chickpea, and rice. Through chromosome location analysis, 37.1% of genes were clustered, and 8 of 9 gene clusters were composed of Tau class members. Through RT-PCR, qRT-PCR and enzyme activity detection, the results showed that the expression of half (20/40) of the tested ZjGSTs was inhibited by phytoplasma infection in field and tissue culture conditions, and GST activity was also significantly reduced. In the resistant and susceptible varieties under phytoplasma infection, ZjGSTU49-ZjGSTU54 in the cluster Ⅳ showed opposite expression patterns, which may be due to functional divergence during evolution. Some upregulated genes (ZjGSTU45, ZjGSTU49, ZjGSTU59, and ZjGSTU70) might be involved in the process of jujube against JWB. The yeast two-hybrid results showed that all 6 Tau-class proteins tested could form homodimers or heterodimers. Overall, the comprehensive analysis of the jujube GST gene family revealed that ZjGSTs responded actively to phytoplasma infection. Furthermore, some screened genes (ZjGSTU24, ZjGSTU49-52, ZjGSTU70, and ZjDHAR10) will contribute to further functional studies of jujube-phytoplasma interactions.

Fruit wart is an important appearance trait influencing consumer preferences of bitter gourd (Momordica charantia L.). The molecular genetic mechanisms underlying fruit wart formation in bitter gourd are largely unknown. In this study, genetic analysis based on four generations showed that fruit wart formation in bitter gourd was controlled by a single dominant locus named as Fwa. The Fwa locus was initially mapped into a 4.82 Mb region on pseudochromosome 4 by BSA-seq analysis and subsequently narrowed down to a 286.30 kb region by linkage analysis. A large F₂ population consisting of 2 360 individuals was used to screen recombinants, and the Fwa locus was finally fine mapped into a 22.70 kb region harboring four protein-coding genes through recombination analysis. MC04g1399, encoding an epidermal patterning factor 2-like protein, was proposed as the best candidate gene for Fwa via sequence variation and expression analysis. In addition, a 1-bp insertion and deletion (InDel) variation within MC04g1399 was converted to a cleaved amplified polymorphic sequence (CAPS) marker that could precisely distinguish between the warty and non-warty types with an accuracy rate of 100% among a wide panel of 126 bitter gourd germplasm resources. Our results not only provide a scientific basis for deciphering the molecular mechanisms underlying fruit wart formation but also provide a powerful tool for efficient genetic improvement of fruit wart via marker-assisted selection.

Auxin is throughout the entire life process of plants and is involved in the crosstalk with other hormones, yet its role in apple disease resistance remains unclear. In this study, we investigated the function of auxin/indole-3-acetic acid (IAA) gene MdIAA24 overexpression in enhancing apple resistance to Glomerella leaf spot (GLS) caused by Colletotrichum fructicola (Cf). Analysis revealed that, upon Cf infection, 35S::MdIAA24 plants exhibited enhanced superoxide dismutase (SOD) and peroxidase (POD) activity, as well as a greater amount of glutathione (reduced form) and ascorbic acid accumulation, resulting in less H₂O₂ and superoxide anion (O₂^.−) in apple leaves. Furthermore, 35S::MdIAA24 plants produced more protocatechuic acid, proanthocyanidins B1, proanthocyanidins B2 and chlorogenic acid when infected with Cf. Following Cf infection, 35S::MdIAA24 plants presented lower levels of IAA and jasmonic acid (JA), but higher levels of salicylic acid (SA), along with the expression of related genes. The overexpression of MdIAA24 was observed to enhance the activity of chitinase and β-1,3-glucanase in Cf-infected leaves. The results indicated the ability of MdIAA24 to regulate the crosstalk between IAA, JA and SA, and to improve reactive oxygen species (ROS) scavenging and defense-related enzymes activity. This jointly contributed to GLS resistance in apple.

The double flower developmental process is regulated via a complex transcriptional regulatory network. To understand this highly dynamic and complex developmental process of Dianthus spp., we performed a comparative analysis of floral morphology and transcriptome dynamics in simple flowers and double flowers. We found that the primordium of double flowers of ‘X’ was larger in size compared to that of simple flowers of ‘L’ in Dianthus chinensis. RNA-seq and Weighted Gene Co-expression Network Analysis (WGCNA) during flower development, identified stage-specific gene network modules. Expression analysis by RNA-seq indicated that a group of genes related to floral meristem identity, primordia position and polarity were highly expressed in double flowers genotypes compared to simple flowers genotypes, suggesting their roles in double-petal formation. A total of 21 DEGs related to petal number were identified between simple and double flowers. The experiments of in situ hybridization revealed that DcaAP2L, DcaLFY and DcaUFO genes were expressed in the intra-sepal boundary and petal boundary. We proposed a potential transcriptional regulatory network for simple and double flower development. This study provides novel insights into the molecular mechanism underlying double flower formation in Dianthus spp.

Cerasus humilis is a kind of economic fruit tree peculiar to China, which is widely used in the food, landscape, and pharmaceutical industries. Anthocyanins are a phenolic metabolite that plays an essential role in fruit coloration. However, the regulatory network of C. humilis in anthocyanin biosynthesis is still unclear. In this study, the R2R3-MYB transcription factor ChMYB1 was isolated from the full genome of the species. Yeast one-hybrid, dual-luciferase assays, and GUS staining showed that ChMYB1 significantly increased anthocyanin contents in C. humilis fruit by promoting the expression of ChCHS and ChUFGT by binding MBS (MYB-binding elements). ChMYB1 interacted with ChbHLH42 and ChTTG1 to form the MBW complex and further enhanced the expression of ChUFGT. In addition, abscisic acid (ABA) treatment promoted the expression of ChMYB1 and anthocyanin accumulation in C. humilis fruit. Interestingly, ABA treatment enhanced the interaction between ChMYB1 and ChbHLH42. Furthermore, ChABI5 inhibited the interaction between ChMYB1 and ChbHLH42. Our data elucidated the primary molecular mechanism of anthocyanin biosynthesis in C. humilis fruit, deepening the understanding of the regulatory network affecting anthocyanin metabolism in edible fruit crops.

There is a close relationship between potassium (K) and nitrogen (N). However, the roles of K under high N conditions remain unclear. Using a hydroponics approach, we monitored the morphological, physiological, and molecular changes in M9T337 apple (Malus domestica) rootstocks under different nitrate (10 and 30 mmol·L⁻¹ ${\text{N}\text{O}}_3^{-}$) and K supply (0.5, 6, 10, and 20 mmol·L⁻¹ K⁺) conditions. Results revealed that high nitrate inhibited the root growth of M9T337 rootstocks, downregulated the expressions of K transporter genes (MdPT5, MdHKT1, and MdATK1), and reduced the net ${\text{N}\text{O}}_3^{-}$ and K⁺ influx at the surface of roots, thereby resulting in an N/K imbalance in rootstocks. Further investigation showed that 10 mmol·L⁻¹ K increased the activity of N metabolic enzymes (NR, GS, NiR, and GOGAT), upregulated the expressions of genes related to nitrate uptake and transport (MdNRT1.1, MdNRT1.2, MdNRT1.5, and MdNRT2.4), promoted ¹⁵N transport from the roots to the shoots, optimized leaf N distribution, and improved photosynthetic N utilization efficiency under high nitrate conditions. These results suggest that the negative effects of high nitrate may be related to the N/K imbalance and that reducing N/K in plants by increasing K supply level can effectively alleviate the inhibition of N assimilation by high nitrate stress.

Melatonin (MT) is a low molecular weight compound with multiple biological functions in plants. It is known to delay leaf senescence in various species. However, no data are available on the MT signaling pathway in postharvest vegetables. This study demonstrates that MT increases cGMP concentration and the expression of the cGMP synthesis gene BcGC1 in pak choi. The cGMP inhibitor LY83583 destroys effect of MT delaying the leaf senescence. LY83583 also prevents MT treatment from reducing the expression of chlorophyll metabolism-related genes (BcNYC1, BcNOL, BcPPH1/2, BcSGR1/2, and BcPAO) and senescence genes (BcSAG12 and BcSAG21). It also inhibits MT from reducing the activity of the key chlorophyll catabolism enzymes Mg-dechelatase, pheophytinase, and pheide a oxygenase. Thus, the ability of MT to maintain high levels of chlorophyll metabolites is also destroyed. The Arabidopsis cGMP synthetic gene mutant atgc1 was used to confirm that delayed leaf senescence caused by MT is mediated, at least in part, by the second messenger cGMP.

Tree peony (Paeonia suffruticosa Andrews) is a well-known ornamental plant with high economic value, but the short fluorescence is a key obstacle to its ornamental value and industry development. High temperature accelerates flower senescence and abscission, but the associated mechanisms are poorly understood. In this study, the tandem mass tag (TMT) proteome and label-free quantitative ubiquitome from tree peony cut flowers treated with 20 °C for 0 h (RT0), 20 °C or 28 °C for 60 h (RT60 or HT60) were examined based on morphological observation, respectively. Totally, 6970 proteins and 1545 lysine ubiquitinated (Kub) sites in 844 proteins were identified. Hydrophilic residues (such as glutamate and aspartate) neighboring the Kub sites were in preference, and 36.01% of the Kub sites were located on the protein surface. The differentially expressed proteins (DEPs) and Kub-DEPs in HT60 vs RT60 were mainly enriched in ribosomal protein, protein biosynthesis, secondary metabolites biosynthesis, flavonoid metabolism, carbohydrate catabolism, and auxin biosynthesis and signaling revealed by GO and KEGG analysis, accompanying the increase of endogenous abscisic acid (ABA) accumulation and decrease of endogenous indoleacetic acid (IAA) level. Additionally, the expression patterns of six enzymes (SAMS, ACO, YUC, CHS, ANS and PFK) putatively with Kub modifications were analyzed by proteome and real-time quantitative RT-PCR. The cell-free degradation assays showed PsSAMS and PsACO proteins could be degraded via the 26 S proteasome system in tree peony flowers. Finally, a working model was proposed for the acceleration of flower senescence and abscission by high temperature. In summary, all results contributed to understanding the mechanism of flower senescence induced by high temperature and prolonging fluorescence in tree peony.

As one of the most widely distributed and highly conserved transcription factors in eukaryotes, basic leucine zipper proteins (bZIPs) are involved in a variety of biological processes in plants, but they are largely unknown in citrus. In this study, 56 bZIP family members were identified genome-wide from an important citrus rootstock, namely trifoliate orange (Poncirus trifoliata L. Raf.), and these putative bZIPs were named PtbZIP1–PtbZIP56. All PtbZIPs were classified into 13 subgroups by phylogenetic comparison with Arabidopsis thaliana bZIPs (AtbZIPs), and they were randomly distributed on nine known (50 genes) chromosomes and one unknown (6 genes) chromosome. Sequence analysis revealed the detailed characteristics of PtPZIPs, including their amino acid length, isoelectric point (pI), molecular weight (MW), predicted subcellular localization, gene structure, and conserved motifs. Prediction of promoter elements suggested the presence of drought, low-temperature, wound, and defense and stress responsive elements, as well as multiple hormone-responsive cis-acting elements. Spatiotemporal expression analysis showed the transcriptional patterns of PtbZIPs in different tissues and under dehydration, high salt, ABA, and IAA treatments. In addition, 21 PtbZIPs were predicted to have direct or indirect protein–protein interactions. Among these, PtbZIP49 was experimentally proven to interact with PtbZIP1 or PtbZIP11 by using a yeast two-hybrid assay and bimolecular fluorescence complementation (BiFC). Subcellular localization analysis further revealed that PtbZIP1, PtbZIP11, and PtbZIP49 were localized in the nucleus. Moreover, PtbZIP49 was functionally identified as having an important role in salt stress via ectopic expression in A. thaliana and silenced in trifoliate orange using virus-induced gene silencing (VIGS). This study provided comprehensive information on PtbZIP transcription factors in citrus and highlights their potential functions in abiotic stress.