Analysis of the thaumatin-like genes of Rosa chinensis and functional analysis of the role of RcTLP6 in salt stress tolerance

RcMYB8 enhances salt and drought tolerance in rose (Rosa chinensis) by modulating RcPR5/1 and RcP5CS1

Plant Myeloblastosis (MYB) proteins function crucially roles upon variegated abiotic stresses. Nonetheless, their effects and mechanisms in rose (Rosa chinensis) are not fully clarified. In this study, we characterized the effects of rose RcMYB8 under salt and drought tolerances. For induction of the RcMYB8 expression, NaCl and drought stress treatment were adopted. Rose plants overexpressing RcMYB8 displayed enhanced tolerance to salinity and drought stress, while silencing RcMYB8 resulted in decreased tolerance, as evidenced by lowered intra-leaf electrolyte leakage and callose deposition, as well as photosynthetic sustainment under stressed conditions. Here, we further show that RcMYB8 binds similarly to the promoters of RcPR5/1 and RcP5C51 in vivo and in vitro. Inhibiting RcP5CS1 by virus-induced gene silencing led to decreased drought tolerance through the reactive oxygen species (ROS) homeostatic regulation. RcP5CS1-silenced plants showed an increase in ion leakage and reduce of proline content, together with the content of malondialdehyde (MDA) increased, lowered activities of Catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD). Our study highlights the transcriptional modulator role of RcMYB8 in drought and salinity tolerances, which bridges RcPR5/1 and RcP5CS1 by promoting ROS scavenging. Besides, it is probably applicable to the rose plant engineering for enhancing their abiotic stress tolerances.

Thaumatin-like protein family genes VfTLP4-3 and VfTLP5 are critical for faba bean's response to drought stress at the seedling stage

Thaumatin-like proteins (TLPs) are a diverse family of pathogenesis-related proteins (PR-5) found in various plant species. Faba bean is an economically important crop known for its nutritional value and resilience to harsh environmental conditions, including drought. In this study, we conducted a comprehensive analysis of the gene structure, phylogenetics, and expression patterns of TLP genes in faba bean, with a specific focus on their response to drought stress. A total of 10 TLP genes were identified and characterized from the faba bean transcriptome, which could be classified into four distinct groups based on their evolutionary relationships. Conserved cysteine residues and REDDD motifs, which are characteristic features of TLPs, were found in most of the identified VfTLP members, and these proteins were likely to reside in the cytoplasm. Two genes, VfTLP4-3 and VfTLP5, exhibited significant upregulation under drought conditions. Additionally, ectopically expressing VfTLP4-3 and VfTLP5 in tobacco leaves resulted in enhanced drought tolerance and increased peroxidase (POD) activity. Moreover, the protein VfTLP4-3 was hypothesized to interact with glycoside hydrolase family 18 (GH18), endochitinase, dehydrin, Barwin, and aldolase, all of which are implicated in chitin metabolism. Conversely, VfTLP5 was anticipated to associate with peptidyl-prolyl cis-trans isomerase-like 3, a molecule linked to the synthesis of proline. These findings suggest that these genes may play crucial roles in mediating the drought response in faba bean through the regulation of these metabolic pathways, and serve as a foundation for future genetic improvement strategies targeting enhanced drought resilience in this economically important crop.

NGS transcriptomic analysis uncovers the possible resistance mechanisms of olive to Spilocea oleagina leaf spot infection

Spilocea oleagina is a dangerous obligate fungal pathogen of olive, feared in the Mediterranean countries, causing Peacock's eye or leaf spot infection, which can lead to a serious yield loss of approximately 20% or higher depending on climatic conditions. Coping with this disease is much more problematic for organic farms. To date, knowledge on the genetic control of possible mechanisms of resistance/low susceptibility is quite limited. In this work, comparative transcriptomic analysis (RNA-seq) was conducted in leaf tissues of a low susceptible cultivar Koroneiki and a high susceptible cultivar Nocellara del Belice, both tested in the field using the NaOH test, considering two stages-"zero sign of disease" and "evident sign of infection". Cultivars showed a very large number of differentially expressed genes (DEGs) in both stages. 'Koroneiki' showed an extensive hormonal crosstalk, involving Abscisic acid (ABA) and ethylene synergistically acting with Jasmonate, with early signaling of the disease and remarkable defense responses against Spilocea through the over-expression of many resistance gene analogs or pathogenesis-related (PR) genes: non-specific lipid-transfer genes (nsLTPs), LRR receptor-like serine/threonine-protein kinase genes, GDSL esterase lipase, defensin Ec-AMP-D2-like, pathogenesis-related leaf protein 6-like, Thaumatin-like gene, Mildew resistance Locus O (MLO) gene, glycine-rich protein (GRP), MADS-box genes, STH-21-like, endochitinases, glucan endo-1,3-beta-glucosidases, and finally, many proteinases. Numerous genes involved in cell wall biogenesis, remodeling, and cell wall-based defense, including lignin synthesis, were also upregulated in the resistant cultivar, indicating the possible role of wall composition in disease resistance. It was remarkable that many transcription factors (TS), some of which involved in Induced Systemic Resistance (ISR), as well as some also involved in abiotic stress response, were found to be uniquely expressed in 'Koroneiki', while 'Nocellara del Belice' was lacking an effective system of defense, expressing genes that overlap with wounding responses, and, to a minor extent, genes related to phenylpropanoid and terpenoid pathways. Only a Thaumatin-like gene was found in both cultivars showing a similar expression. In this work, the genetic factors and mechanism underlying the putative resistance trait against this fungal pathogen were unraveled for the first time and possible target genes for breeding resistant olive genotypes were found.

Genome-Wide Identification and Characterization of the TLP Gene Family in Phyllostachys edulis and Association with Witches' Broom Disease Resistance in Bamboo

Thaumatin-like proteins (TLPs) are pathogenesis-related proteins with pivotal roles in plant defense mechanisms. In this study, various bioinformatics and RNA-seq methods were used to analyze the biotic and abiotic stress responses of the TLP family in Phyllostachys edulis. Overall, 81 TLP genes were identified in P. edulis; 166 TLPs from four plant species were divided into three groups and ten subclasses, with genetic covariance observed between these species. Subcellular localization in silico studies indicated that TLPs were primarily distributed in the extracellular. Analysis of the upstream sequences of TLPs demonstrated the presence of cis-acting elements related to disease defense, environmental stress, and hormonal responses. Multiple sequence alignment demonstrated that most TLPs possessed five conserved REDDD amino acid sequences with only a few amino acid residue differences. RNA-seq analysis of P. edulis responses to Aciculosporium take, the pathogenic fungus that causes witches' broom disease, showed that P. edulis TLPs (PeTLPs) were expressed in different organs, with the highest expression in buds. PeTLPs responded to both abscisic acid and salicylic acid stress. These PeTLP expression patterns were consistent with their gene and protein structures. Collectively, our findings provide a basis for further comprehensive analyses of the genes related to witches' broom in P. edulis.

RcbHLH59-RcPRs module enhances salinity stress tolerance by balancing Na+/K+ through callose deposition in rose (Rosa chinensis)

Basic helix-loop-helix (bHLH) proteins play pivotal roles in plant growth, development, and stress responses. However, the molecular and functional properties of bHLHs have not been fully characterized. In this study, a novel XI subgroup of the bHLH protein gene RcbHLH59 was isolated and identified in rose (Rosa sp.). This gene was induced by salinity stress in both rose leaves and roots, and functioned as a transactivator. Accordingly, silencing RcbHLH59 affected the antioxidant system, Na ⁺/K ⁺ balance, and photosynthetic system, thereby reducing salt tolerance, while the transient overexpression of RcbHLH59 improved salinity stress tolerance. Additionally, RcbLHLH59 was found to regulate the expression of sets of pathogenesis-related (PR) genes in RcbHLH59-silenced (TRV-RcbHLH59) and RcbHLH59-overexpressing (RcbHLH59-OE) rose plants. The RcPR4/1 and RcPR5/1 transcript levels showed opposite changes in the TRV-RcbHLH59 and RcbHLH59-OE lines, suggesting that these two genes are regulated by RcbHLH59. Further analysis revealed that RcbHLH59 binds to the promoters of RcPR4/1 and RcPR5/1, and that the silencing of RcPR4/1 or RcPR5/1 led to decreased tolerance to salinity stress. Moreover, callose degradation- and deposition-related genes were impaired in RcPR4/1- or RcPR5/1-silenced plants, which displayed a salt tolerance phenotype by balancing the Na⁺/K⁺ ratio through callose deposition. Collectively, our data highlight a new RcbLHLH59-RcPRs module that positively regulates salinity stress tolerance by balancing Na⁺/K⁺ and through callose deposition in rose plants.

Genome-wide analysis of the Thaumatin-like gene family in Qingke (Hordeum vulgare L. var. nudum) uncovers candidates involved in plant defense against biotic and abiotic stresses

Thaumatin-like proteins (TLPs) participate in the defense responses of plants as well as their growth and development processes, including seed germination. Yet the functioning of TLP family genes, in addition to key details of their encoded protein products, has not been thoroughly investigated for Qingke (Hordeum vulgare L. var. nudum). Here, a total of 36 TLP genes were identified in the genome of Qingke via HMM profiling. Of them, 25 TLPs contained a signal peptide at the N-terminus, with most proteins predicted to localize in the cytoplasm or outer membrane. Sequence alignment and motif analysis revealed that the five REDDD residues required for β-1,3-glucanase activity were conserved in 21 of the 36 Qingke TLPs. Phylogenetically, the TLPs in plants are clustered in 10 major groups. Our analysis of gene structure did not detect an intron in 15 Qingke TLPs whereas the other 21 did contain 1-7 introns. A diverse set of cis-acting motifs were found in the promoters of the 36 TLPs, including elements related to light, hormone, and stress responses, growth and development, circadian control, and binding sites of transcription factors, thus suggesting a multifaceted role of TLPs in Qingke. Expression analyses revealed the potential involvement of TLPs in plant defense against biotic and abiotic stresses. Taken together, the findings of this study deepen our understanding of the TLP family genes in Qingke, a staple food item in Tibet, which could strengthen future investigations of protein function in barley and its improved genetic engineering.

Thaumatin-like Protein (TLP) Genes in Garlic (Allium sativum L.): Genome-Wide Identification, Characterization, and Expression in Response to Fusarium proliferatum Infection

Plant antifungal proteins include the pathogenesis-related (PR)-5 family of fungi- and other stress-responsive thaumatin-like proteins (TLPs). However, the information on the TLPs of garlic (Allium sativum L.), which is often infected with soil Fusarium fungi, is very limited. In the present study, we identified 32 TLP homologs in the A. sativum cv. Ershuizao genome, which may function in the defense against Fusarium attack. The promoters of A. sativumTLP (AsTLP) genes contained cis-acting elements associated with hormone signaling and response to various types of stress, including those caused by fungal pathogens and their elicitors. The expression of AsTLP genes in Fusarium-resistant and -susceptible garlic cultivars was differently regulated by F. proliferatum infection. Thus, in the roots the mRNA levels of AsTLP7–9 and 21 genes were increased in resistant and decreased in susceptible A. sativum cultivars, suggesting the involvement of these genes in the garlic response to F. proliferatum attack. Our results provide insights into the role of TLPs in garlic and may be useful for breeding programs to increase the resistance of Allium crops to Fusarium infections.