VqDUF642, a gene isolated from the Chinese grape Vitis quinquangularis, is involved in berry development and pathogen resistance

Antibody array-based proteome approach reveals proteins involved in grape seed development

Grape (Vitis vinifera) is one of the most widely cultivated fruits globally, primarily used for processing and fresh consumption. Seedless grapes are favored by consumers for their convenience, making the study of seedlessness a subject of great interest to scientists. To identify regulators involved in this process in grape, a monoclonal antibody (mAb)-array-based proteomics approach, which contains 21,120 mAbs, was employed for screening proteins/antigens differentially accumulated in grape during development. Differences in antigen signals were detected between seeded and seedless grapes revealing the differential accumulation of 2,587 proteins. After immunoblotting validation, 71 antigens were further immunoprecipitated and identified by mass spectrometry (MS). An in planta protein-protein interaction (PPI) network of those differentially accumulated proteins was established using mAb antibody by immunoprecipitation (IP)-MS, which reveals the alteration of pathways related to carbon metabolism and glycolysis. To validate our result, a seedless-related protein, DUF642 domain-containing protein (VvDUF642), which is functionally uncharacterized in grapes, was ectopically overexpressed in tomato (Solanum lycopersicum "MicroTom") and led to a reduction in seed production. PPI network indicated that VvDUF642 interacts with pectin acetylesterase (VvPAE) in grapes, which was validated by BiFC and Co-IP. As anticipated, overexpression of VvPAE substantially reduced seed production in tomato. Moreover, S. lycopersicum colourless non-ripening expression was altered in VvDUF642- and VvPAE-overexpressing plants. Taken together, we provided a high-throughput method for the identification of proteins involved in the seed formation process. Among those, VvDUF642 and VvPAE are potential targets for breeding seedless grapes and other important fruits in the future.

Methylesterification of cell-wall pectin controls the diurnal flower-opening times in rice

Flowers are the core reproductive organ of plants, and flowering is essential for cross-pollination. Diurnal flower-opening time is thus a key trait influencing reproductive isolation, hybrid breeding, and thermostability in plants. However, the molecular mechanisms controlling this trait remain unknown. Here, we report that rice Diurnal Flower Opening Time 1 (DFOT1) modulates pectin methylesterase (PME) activity to regulate pectin methylesterification levels of the lodicule cell walls, which affect lodicule swelling to control diurnal flower-opening time. DFOT1 is specifically expressed in the lodicules, and its expression gradually increases with the approach to flowering but decreases with flowering. Importantly, a knockout of DFOT1 showed earlier diurnal flower opening. We demonstrate that DFOT1 interacts directly with multiple PMEs to promote their activity. Knockout of PME40 also resulted in early diurnal flower opening, whereas overexpression of PME42 delayed diurnal flower opening. Lower PME activity was observed to be associated with higher levels of pectin methylesterification and the softening of cell walls in lodicules, which contribute to the absorption of water by lodicules and cause them to swell, thus promoting early diurnal flower opening. Higher PME activity had the opposite effect. Collectively, our work uncovers a molecular mechanism underlying the regulation of diurnal flower-opening time in rice, which would help reduce the costs of hybrid breeding and improve the heat tolerance of flowering plants by avoiding higher temperatures at anthesis.

Emergent Ascomycetes in Viticulture: An Interdisciplinary Overview

The reduction of pesticide usage is a current imperative and the implementation of sustainable viticulture is an urgent necessity. A potential solution, which is being increasingly adopted, is offered by the use of grapevine cultivars resistant to its main pathogenic threats. This, however, has contributed to changes in defense strategies resulting in the occurrence of secondary diseases, which were previously controlled. Concomitantly, the ongoing climate crisis is contributing to destabilizing the increasingly dynamic viticultural context. In this review, we explore the available knowledge on three Ascomycetes which are considered emergent and causal agents of powdery mildew, black rot and anthracnose. We also aim to provide a survey on methods for phenotyping disease symptoms in fields, greenhouse and lab conditions, and for disease control underlying the insurgence of pathogen resistance to fungicide. Thus, we discuss fungal genetic variability, highlighting the usage and development of molecular markers and barcoding, coupled with genome sequencing. Moreover, we extensively report on the current knowledge available on grapevine-ascomycete interactions, as well as the mechanisms developed by the host to counteract the attack. Indeed, to better understand these resistance mechanisms, it is relevant to identify pathogen effectors which are involved in the infection process and how grapevine resistance genes function and impact the downstream cascade. Dealing with such a wealth of information on both pathogens and the host, the horizon is now represented by multidisciplinary approaches, combining traditional and innovative methods of cultivation. This will support the translation from theory to practice, in an attempt to understand biology very deeply and manage the spread of these Ascomycetes.

Transcription factor VqERF114 regulates stilbene synthesis in Chinese wild Vitis quinquangularis by interacting with VqMYB35

VqERF114 regulates stilbene synthesis by interacting with VqMYB35. Resveratrol is a stilbene, an important class of secondary metabolites that accumulates in some plant species, including grapevine. In the plant, these are involved in the response to attack by plant pathogens and, as a component of the human diet, they offer a range of significant health benefits. Stilbene synthase (STS), the key enzyme responsible for resveratrol synthesis, has been characterised in a small number of plant species. However, the regulatory mechanisms for stilbene synthesis are uncertain. Here, an ERF family transcription factor from Chinese wild Vitis quinquangularis, VqERF114, was characterised as an indirect regulator of stilbene synthesis. A transient overexpression assay of VqERF114 in grapevine leaves led to increased STS expression and stilbene accumulation. However, VqERF114 did not bind to the promoters of VqSTSs but the MYB transcription factor, VqMYB35, did interact with VqERF114. This interaction was confirmed by a yeast two-hybrid assay and bimolecular fluorescence complementation. Furthermore, VqMYB35 showed activation effects on the expressions of VqSTS15, VqSTS28, VqSTS42 and VqSTS46 by binding directly to the MBS elements in their promoters. Co-overexpression of VqERF114 and VqMYB35 resulted in higher VqSTSs expression and more stilbene synthesis. These results demonstrate that VqERF114 regulates stilbene synthesis by interacting with VqMYB35.

Overview of the Role of Cell Wall DUF642 Proteins in Plant Development

The DUF642 protein family is found exclusively in spermatophytes and is represented by 10 genes in Arabidopsis and in most of the 24 plant species analyzed to date. Even though the primary structure of DUF642 proteins is highly conserved in different spermatophyte species, studies of their expression patterns in Arabidopsis have shown that the spatial-temporal expression pattern for each gene is specific and consistent with the phenotypes of the mutant plants studied so far. Additionally, the regulation of DUF642 gene expression by hormones and environmental stimuli was specific for each gene, showing both up- and down-regulation depending of the analyzed tissue and the intensity or duration of the stimuli. These expression patterns suggest that the DUF642 genes are involved throughout the development and growth of plants. In general, changes in the expression patterns of DUF642 genes can be related to changes in pectin methyl esterase activity and/or to changes in the degree of methyl-esterified homogalacturonans during plant development in different cell types. Thus, the regulation of pectin methyl esterases mediated by DUF642 genes could contribute to the regulation of the cell wall properties during plant growth.

Cell Wall Localization of Two DUF642 Proteins, BIIDXI and TEEBE, during Meloidogyne incognita Early Inoculation

The root-knot nematode Meloidogyne incognita infects a variety of plants, including Arabidopsis thaliana. During migration, root-knot nematodes secrete different proteins to modify cell walls, which include pectolytic enzymes. However, the contribution of host cell wall proteins has not been described during this process. The function of two DUF642 cell wall proteins, BIIDXI (BDX, At4g32460) and TEEBE (TEB, At2g41800), in plant development could be related to the regulation of pectin methyl esterification status in the cell walls of different tissues. Accordingly, the expression of these two genes is up-regulated by auxin. BDX and TEB were highly induced during early M. incognita inoculation. Moreover, cell wall localization of the proteins was also induced. The cell wall localization of BDX and TEB DUF642 proteins during M. incognita early inoculation suggested that these two proteins could be involved in the regulation of the degree of pectin methylation during cell separation.

Degree of pectin methyl esterification in endosperm cell walls is involved in embryo bending in Arabidopsis thaliana

The endosperm is a transitory structure involved in proper embryo elongation. The cell walls of mature seed endosperm are generally composed of a uniform distribution of cellulose, unesterified homogalacturonans, and arabinans. Recent studies suggest that changes in cell wall properties during endosperm development could be related to embryo growth. The degree of methyl esterification of homogalacturonans may be involved in this endosperm tissue remodelling. The relevance of the degree of homogalacturonan methyl esterification during seed development was determined by immunohistochemical analyses using a panel of probes with specificity for homogalaturonans with different degrees of methyl esterification. Low-esterified and un-esterified homogalacturonans were abundant in endosperm cells during embryo bending and were also detected in mature embryos. BIDXII (BDX) could be involved in seed development, because bdx-1 mutants had misshapen embryos. The methyl esterification pattern described for WT seeds was different during bdx-1 seed development; un-esterified homogalacturonans were scarcely present in the cell walls of endosperm in bending embryos and mature seeds. Our results suggested that the degree of methyl esterification of homogalacturonans in the endosperm cell wall may be involved in proper embryo development.

Molecular cloning of a CC-NBS-LRR gene from Vitis quinquangularis and its expression pattern in response to downy mildew pathogen infection

Downy mildew, caused by Plasmopara viticola, can result in a substantial decrease in grapevine productivity. Vitis vinifera is a widely cultivated grapevine species, which is susceptible to this disease. Repeated pesticide applications are harmful for both the environment and human health. Thus, it is essential to develop varieties/cultivars that are resistant to downy mildew and other diseases. In our previous studies, we investigated the natural resistance of the Chinese wild grapevine V. quinquangularis accession 'PS' against P. viticola and obtained several candidate resistance (R) genes that may play important roles in plant disease resistance. In the present study, we isolated a CC-NBS-LRR-type R gene from 'PS' and designated it VqCN. Its open reading frame is 2676 bp which encodes a protein of 891 amino acids with a predicted molecular mass of 102.12 kDa and predicted isoelectric point of 6.53. Multiple alignments with other disease resistant (R) proteins revealed a conserved phosphate-binding loop (P-loop), resistance nucleotide binding site, a hydrophobic domain (GLPL) and methionine-histidine-aspartate (MHD) motifs, which are typical components of nucleotide-binding site leucine-rich repeat proteins, as well as a coiled-coil region in the N-terminus. Quantitative real-time polymerase chain reaction analysis showed that the transcript of VqCN was rapidly and highly induced after infection with P. viticola in 'PS'. Moreover, the leaves of susceptible 'Cabernet Sauvignon' transiently expressing VqCN manifested increased resistance to P. viticola. The results indicated that VqCN might play a positive role in protecting grapevine against infection with P. viticola. Cloning and functional analysis of a putative resistance gene provide a basis for disease-resistance breeding.

The cell wall DUF642 At2g41800 (TEB) protein is involved in hypocotyl cell elongation

In plants, the cell wall is a complex and dynamic structure comprising high molecular weight carbohydrates and proteins. The cell wall plays an important role in several stages of the plant life cycle, including cell division, elongation and differentiation. The DUF642 family of cell wall proteins is highly conserved in spermatophytes and might be involved in pectin structural modifications. Particularly, At2g41800 is one of the most highly induced genes during the M/G1 phases of the cell cycle, and the protein encodes by this gene has been detected in cell wall proteomes of cell suspension cultures. In the present study, the expression of At2g41800 (TEB) was confirmed in primary and lateral roots, stigmatic papillae and hypocotyls. Subcellular localization studies showed that TEB is located in the cell wall. The root length and lateral root density were not affected in either of the two teb mutants studied, but the length of the hypocotyls from seedlings grown under light and dark conditions was increased. Immunogold labelling studies using JIM5 antibodies on sections of hypocotyl epidermal cells showed an important reduction of gold particles in teb mutants. The results suggested that TEB is involved in hypocotyl elongation.