Molecular Horticulture最新文献

5-Aminolevulinic acid (ALA), as a natural plant growth regulator, is well known for promoting red fruit coloring by enhancing anthocyanin accumulation. However, the underlying mechanisms remain elusive. In this study, we firstly demonstrated that ALA upregulates gene expression of the transcription factor MdMADS1, which in turn directly binds to and activates transcription of the key anthocyanin biosynthetic genes, MdCHS and MdUFGT. Then, we identified a novel WRKY transcription factor, MdWRKY71, that interacts with MdMADS1. Through gene manipulation, we revealed that MdWRKY71 plays a pivotal role in ALA-induced anthocyanin accumulation, highlighting its regulatory significance in this process. Further investigation unveiled that MdWRKY71 not only activates MdMADS1 transcription but also enhances its transcriptional activation on its target genes, MdCHS and MdUFGT. Additionally, we discovered that MdWRKY71 independently binds to and activates the transcription of two other anthocyanin biosynthetic genes, MdANS and MdDFR. The protein-protein interaction between MdWRKY71 and MdMADS1 amplifies the transcriptional activation of these genes by MdWRKY71. These findings delineate a fine and complex regulatory framework where MdWRKY71 and MdMADS1 coordinately regulate anthocyanin biosynthesis in apples, providing new insights into the molecular control of fruit coloration and offering potential target genes for breeding aimed at enhancing fruit quality.

Organic acid is a crucial indicator of fruit quality traits. Citric acid, the predominant organic acid in citrus fruit, directly influences its edible quality and economic value. While the transcriptional regulatory mechanisms of citric acid metabolism have been extensively studied, the understanding about the transcriptional and epigenetic co-regulation mechanisms is limited. This study characterized a transcription factor, CitGATA7, which directly binds to and activates the expression of genes associated with the glutamine synthetase pathway regulating citric acid degradation. These genes include the aconitase encoding gene CitACO3, the isocitrate dehydrogenase encoding gene CitIDH1, and the glutamine synthetase encoding gene CitGS1. Furthermore, CitGATA7 physically interacts with the histone acetyltransferase CitHAG28 to enhance histone 3 acetylation levels near the transcription start site of CitACO3, CitIDH1, and CitGS1, thereby increasing their transcription and promoting citric acid degradation. The findings demonstrate that the CitGATA7-CitHAG28 protein complex transcriptionally regulate the expression of the GS pathway genes, i.e., CitACO3, CitIDH1, and CitGS1, via histone acetylation, thus promoting citric acid catabolism. This study establishes a direct link between transcriptional regulation and histone acetylation regarding citric acid metabolism, providing insights for strategies to manipulate organic acid accumulation in fruit.

Sorbitol is an important primary metabolite that serves as both a carbon source and signal to pathogens. The leaf diseases caused by Alternata alternata are particularly serious in crabapple (Malus micromalus). Here, we found that sorbitol can enhance the resistance of crabapple to A. alternata R1 by increasing the content of flavonoid catechin. Nanomaterials as an emerging technology tool can efficiently deliver lncRNA to target cells. Here, we found nanoencapsulated lncRNA809 (SPc/lncRNA809) exhibits significant resistance to R1strain. To elucidate the effect of SPc/lncRNA809 on flavonoids catechin synthesis, we observed the expression of lncRNA809 was consistent with that of MmNAC17 which regulates the synthesis of catechin and both could jointly respond to sorbitol. MmNAC17 induced the accumulation of catechin in vivo by directly activating the expression of catechin synthase genes MmF3H and MmLAR. Correspondingly, overexpression of lncRNA809 significantly upregulated the expression of MmNAC17 and enhanced the disease resistance. This study reveals for the first time that sorbitol positively regulates the expression of MmNAC17 through lncRNA809, promoting the accumulation of catechin via the expression of MmF3H and MmLAR, ultimately improving the defense response of M. micromalus. This research provides a crucial foundation for the establishment and application of sorbitol-based signaling regulatory networks.

Kiwifruit is an economically and nutritionally important horticultural fruit crop worldwide. The genomic data of several kiwifruit species have been released, providing an unprecedented opportunity for pan-genome analysis to comprehensively investigate the inter- and intra-species genetic diversity and facilitate utilization for kiwifruit breeding. Here, we generated a kiwifruit super pan-genome using 15 high-quality assemblies of eight Actinidia species. For gene-based pan-genome, a total of 61,465 gene families were identified, and the softcore and dispensable genes were enriched in biological processes like response to endogenous stimulus, response to hormone and cell wall organization or biogenesis. Then, structural variations (SVs) against A. chinensis 'Donghong' were identified and then used to construct a graph-based genome. Further population-scale SVs based on resequencing data from 112 individuals of 20 species revealed extensive SVs which probably contributed to the phenotypic diversity among the Actinidia species. SV hotspot regions were found contributed to environmental adaptation. Furthermore, we systematically identified resistance gene analogs (RGAs) in the 15 assemblies and generated a pan-RGA dataset to reveal the diversity of genes potentially involved in disease resistance in Actinidia. The pan-genomic data obtained here is useful for evolutionary and functional genomic studies in Actinidia, and facilitates breeding design.

Peptide hormones are defined as small secreted polypeptide-based intercellular communication signal molecules. Such peptide hormones are encoded by nuclear genes, and often go through proteolytic processing of preproproteins and post-translational modifications. Most peptide hormones are secreted out of the cell to interact with membrane-associated receptors in neighboring cells, and subsequently activate signal transductions, leading to changes in gene expression and cellular responses. Since the discovery of the first plant peptide hormone, systemin, in tomato in 1991, putative peptide hormones have continuously been identified in different plant species, showing their importance in both short- and long-range signal transductions. The roles of peptide hormones are implicated in, but not limited to, processes such as self-incompatibility, pollination, fertilization, embryogenesis, endosperm development, stem cell regulation, plant architecture, tissue differentiation, organogenesis, dehiscence, senescence, plant-pathogen and plant-insect interactions, and stress responses. This article, collectively written by researchers in this field, aims to provide a general overview for the discoveries, functions, chemical natures, transcriptional regulations, and post-translational modifications of peptide hormones in plants. We also updated recent discoveries in receptor kinases underlying the peptide hormone sensing and down-stream signal pathways. Future prospective and challenges will also be discussed at the end of the article.

Flesh firmness is a core quality trait in apple breeding because of its correlation with ripening and storage. Quantitative trait loci (QTLs) were analyzed through bulked segregant analysis sequence (BSA-seq) and comparative transcriptome analysis (RNA-seq) to explore the genetic basis of firmness formation. In this study, phenotypic data were collected at harvest from 251 F₁ hybrids derived from 'Ruiyang' and 'Scilate', the phenotype values of flesh firmness at harvest were extensively segregated for two consecutive years. A total of 11 candidate intervals were identified on chromosomes 03, 05, 06, 07, 13, and 16 via BSA-seq analysis. We characterized a major QTL on chromosome 16 and selected a candidate gene encoding expansin MdEXP-A1 by combining RNA-seq analysis. Furthermore, the genotype of Del-1166 (homozygous deletion) in the MdEXP-A1 promoter was closely associated with the super-hard phenotype of F₁ hybrids, which could be used as a functional marker for marker-assisted selection (MAS) in apple. Functional identification revealed that MdEXP-A1 positively expedited fruit softening in both apple fruits and tomatoes that overexpressed MdEXP-A1. Moreover, the promoter sequence of TE-1166 was experimentally validated containing two binding motifs of MdNAC1, and the absence of the MdEXP-A1 promoter fragment reduced its transcription activity. MdNAC1 also promotes the expression of MdEXP-A1, indicating its potential modulatory role in quality breeding. These findings provide novel insight into the genetic control of flesh firmness by MdEXP-A1.

Banana is sensitive to cold stress and often suffers from chilling injury with browning peel and failure to normal ripening. We have previously reported that banana chilling injury is accompanied by a reduction of miR528 accumulation, alleviating the degradation of its target gene MaPPO and raising ROS levels that cause peel browning. Here, we further revealed that the miR528-MaPPO cold-responsive module was regulated by miR156-targeted SPL transcription factors, and the miR156c-MaSPL4 module was also responsive to cold stress in banana. Transient overexpression of miR156c resulted in a more severe chilling phenotype by decreasing the expression of MaSPL4 and miR528. Conversely, the browning was alleviated in STTM-miR156c silencing and OE-MaSPL4 samples. Furthermore, DNA affinity purification sequencing and MaSPL4-overexpressing transcriptome jointly revealed that MaSPL4 may mediate the transcription of genes related to lipid metabolism and antioxidation, in addition to the miR528-MaPPO module, demonstrating MaSPL4 as a master regulator in the fruit cold response network. In summary, our results suggest that the miR156c-MaSPL4 module can mediate the chilling response in banana by regulating the miR528-MaPPO module and multiple other pathways, which provides evidence for the crosstalk between TFs and miRNAs that can be used for the molecular breeding of fruit cold tolerance.