Uninfected Plant Research Articles

Cowpea lipid transfer protein 1 regulates plant defense by inhibiting the cysteine protease of cowpea mosaic virus

Many virus genomes encode proteases that facilitate infection. The molecular mechanism of plant recognition of viral proteases is largely unexplored. Using the system of Vigna unguiculata and cowpea mosaic virus (CPMV), we identified a cowpea lipid transfer protein (LTP1) which interacts with CPMV-encoded 24KPro, a cysteine protease, but not with the enzymatically inactive mutant 24KPro(C166A). Biochemical assays showed that LTP1 inhibited 24KPro proteolytic cleavage of the coat protein precursor large coat protein-small coat protein. Transient overexpression of LTP1 in cowpea reduced CPMV infection, whereas RNA interference-mediated LTP1 silencing increased CPMV accumulation in cowpea. LTP1 is mainly localized in the apoplast of uninfected plant cells, and after CPMV infection, most of the LTP1 is relocated to intracellular compartments, including chloroplast. Moreover, in stable LTP1-transgenic Nicotiana benthamiana plants, LTP1 repressed soybean mosaic virus (SMV) nuclear inclusion a protease activity, and accumulation of SMV was significantly reduced. We propose that cowpea LTP1 suppresses CPMV and SMV accumulation by directly inhibiting viral cysteine protease activity.

The underground world of plant disease: Rhizosphere dysbiosis reduces above-ground plant resistance to bacterial leaf spot and alters plant transcriptome.

Just as the human gut microbiome is colonized by a variety of microbes, so too is the rhizosphere of plants. An imbalance in this microbial community, known as dysbiosis, can have a negative impact on plant health. This study sought to explore the effect of rhizosphere dysbiosis on the health of tomato plants (Solanum lycopersicum L.), using them and the foliar bacterial spot pathogen Xanthomonas perforans as model organisms. The rhizospheres of 3-week-old tomato plants were treated with either streptomycin or water as a control, and then spray-inoculated with X. perforans after 24 h. Half of the plants that were treated with both streptomycin and X. perforans received soil microbiome transplants from uninfected plant donors 48 h after the streptomycin was applied. The plants treated with streptomycin showed a 26% increase in disease severity compared to those that did not receive the antibiotic. However, the plants that received the soil microbiome transplant exhibited an intermediate level of disease severity. The antibiotic-treated plants demonstrated a reduced abundance of rhizobacterial taxa such as Cyanobacteria from the genus Cylindrospermum. They also showed a down-regulation of genes related to plant primary and secondary metabolism, and an up-regulation of plant defence genes associated with induced systemic resistance. This study highlights the vital role that beneficial rhizosphere microbes play in disease resistance, even against foliar pathogens.

Comparison of photosynthetic pigments and carbohydrate contents in fungus-infected juniper plant (Juniperus phoenicea L.) and the uninfected plant

This study aimed to compare the physiological characteristics of a fungus-infected juniper plant with another healthy plant, these characteristics include photosynthetic pigment content, soluble sugars and sucrose content. The present study revealed the presence of 4 genera of fungi belonging to Ascomycetae and Deuteromycetes isolated from the leaves of Juniperus phoenicea L. and identified by morphological and microscopic characteristics. The species of fungi isolated from the juniper plant are Alternaria alternate, Aspergillus niger, Fusarium oxysporum, Penicillium crustaceum. The affected juniper plant contained 0.306, 0.296 and 0.351 mg g -1 FW chlorophyll a and b and a carotenoid, respectively. The observed decrease in photosynthetic pigment content in the affected plant compared to the healthy plant was 0.713, 0.695 and 0.874 mg g -1 FW, respectively. The content of soluble sugars in juniper plants was measured and found to be 2.26 mg g -1 FW in healthy plants and 1.937 mg g -1 FW in infected plants. The sucrose content was 2.938 mg g -1 FW in the pathogen infected plant and 3.28 mg g -1 FW in the healthy plant. There was a very significant decrease because the sugars are attached to photosynthetic pigments, and as the amount of pigments decreases, the amount of sugars decreases.

Spatial co-transcriptomics reveals discrete stages of the arbuscular mycorrhizal symbiosis

The symbiotic interaction of plants with arbuscular mycorrhizal (AM) fungi is ancient and widespread. Plants provide AM fungi with carbon in exchange for nutrients and water, making this interaction a prime target for crop improvement. However, plant–fungal interactions are restricted to a small subset of root cells, precluding the application of most conventional functional genomic techniques to study the molecular bases of these interactions. Here we used single-nucleus and spatial RNA sequencing to explore both Medicago truncatula and Rhizophagus irregularis transcriptomes in AM symbiosis at cellular and spatial resolution. Integrated, spatially registered single-cell maps revealed infected and uninfected plant root cell types. We observed that cortex cells exhibit distinct transcriptome profiles during different stages of colonization by AM fungi, indicating dynamic interplay between both organisms during establishment of the cellular interface enabling successful symbiosis. Our study provides insight into a symbiotic relationship of major agricultural and environmental importance and demonstrates a paradigm combining single-cell and spatial transcriptomics for the analysis of complex organismal interactions.

Trade-off between local replication and long-distance dissemination during experimental evolution of a satellite RNA.

Satellite RNAs (satRNAs) are molecular parasites that depend on their non-homologous helper viruses (HVs) for essential biological functions. While there are multiple molecular and phylogenetic studies on satRNAs, there is no experimental evolution study on how satRNAs may evolve in common infection conditions. In this study, we serially passaged the Bamboo mosaic virus (BaMV) associated-satRNA (satBaMV) under conditions in which satBaMV either coinfects an uninfected host plant, Nicotiana benthamiana, with BaMV or superinfects a transgenic N. benthamiana expressing the full-length BaMV genome. Single-nucleotide polymorphisms (SNPs) of satBaMV populations were analyzed by deep sequencing. Forty-eight SNPs were identified across four different experimental treatments. Most SNPs are treatment-specific, and some are also ephemeral. However, mutations at positions 30, 34, 63, and 82, all located at the 5' untranslated region (UTR), are universal in all treatments. These universal SNPs are configured into several haplotypes and follow different population dynamics. We constructed isogenic satBaMV strains only differing at positions 30 and 82 and conducted competition experiments in protoplasts and host plants. We found that the haplotype that reached high frequency in protoplasts and inoculation leaves also exhibited poor dissemination to systemic leaves and vice versa, thus suggesting an apparent trade-off between local replication and long-distance dissemination. We posit that the trade-off is likely caused by antagonistic pleiotropy at the 5' UTR. Our findings revealed a hitherto under-explored connection between satRNA genome replication and movement within a host plant. The significance of such a connection during satRNA evolution warrants a more thorough investigation.

Kök lezyon nematodlarının (Pratylenchus thornei) nohut bitkisinin rhizobium bakterileri üzerinde etkisi

Chickpea (Cicer arietinum) is one of the most significant legume crops and supply high-quality protein for human nutrition. legume crops such as chickpea are important agriculturally because of their symbiotic ability to nitrogen fixation with specific soil bacteria. Legumes like chickpea depend on nitrogen provided by the activity to grow, but these rhizobium bacteria are affected by plant-parasitic nematodes that cause less activity and decrease the number of nodules in the chickpea plant. The root-lesion nematodes (Pratylenchus thornei) are common and economically important pests described as one of the major limiting factors in agriculture and the growing chickpea field in the world. In this study, the effects of this nematode on the number of rhizobia (nodules) and rhizobium bacteria activity were assessed in both wild and domesticated accession of Cicer species under laboratory conditions. We inoculated all Cicer accession with the Mesorhizobium bacteria and with one species of the genus Pratylenchus (P. thornei). The result showed that P. thornei has a negative impact on the number of nodules and the activity of rhizobium bacteria. Nematode infection on chickpea caused decreased nodulation. Where, nematode infected plant formed 4-8 nodules/root and less nodule number than an uninfected plant.

Identification of DIR1-Dependant Cellular Responses in Guard Cell Systemic Acquired Resistance.

After localized invasion by bacterial pathogens, systemic acquired resistance (SAR) is induced in uninfected plant tissues, resulting in enhanced defense against a broad range of pathogens. Although SAR requires mobilization of signaling molecules via the plant vasculature, the specific molecular mechanisms remain elusive. The lipid transfer protein defective in induced resistance 1 (DIR1) was identified in Arabidopsis thaliana by screening for mutants that were defective in SAR. Here, we demonstrate that stomatal response to pathogens is altered in systemic leaves by SAR, and this guard cell SAR defense requires DIR1. Using a multi-omics approach, we have determined potential SAR signaling mechanisms specific for guard cells in systemic leaves by profiling metabolite, lipid, and protein differences between guard cells in the wild type and dir1-1 mutant during SAR. We identified two long-chain 18 C and 22 C fatty acids and two 16 C wax esters as putative SAR-related molecules dependent on DIR1. Proteins and metabolites related to amino acid biosynthesis and response to stimulus were also changed in guard cells of dir1-1 compared to the wild type. Identification of guard cell-specific SAR-related molecules may lead to new avenues of genetic modification/molecular breeding for disease-resistant plants.

Newly identified Fusarium strains (olowILH1 and olowILH2) causing ear rot of maize and their control using Glomus clarum and G. deserticola

This study focused on characterization of common Fusarium strains causing ear rot disease of maize and potentials of controlling them using arbuscular mycorrhiza (Glomus clarum Nicol. & Sch. and G. deserticola Trappe, Bloss & Menge). Maize ear showing rot symptoms were obtained from ten (10) different farms in Osun State, Nigeria using random sampling technique and subjected to fungal isolation. The two dominant and most virulent strains (olowILH1 and olowILH2) were further characterized based on morphological and molecular ITS-amplification methods. Responses of maize varieties PVASYN8F2, T2LCOMP1STRSYN-W-1 and T2LCOMP.4 from different agro-ecological zones to selected Fusarium ear rot pathogens and biocontrol efficacy of mycorrhizal fungi were further assessed on growth, yield, and symptoms observed. Selected ear rot pathogens were identified as Fusarium napiforme, they exhibited varying inhibitory effects on tested maize varieties compare to the control (uninfected plant) which had better growth characteristics. T2LCOMP4 was more susceptible to both fungal strains as compared to the other maize varieties (T2LCOMP1STRSYN-W-1 and T2LCOMP4). It was further observed that treatment of most susceptible maize variety (T2LCOMP4) with both arbuscular mycorrhizal fungi in-vivo yielded better suppression of ear rot disease, although Glomus clarum had higher antagonistic/control effect on these pathogens as compared to G. deserticola.

Plant biotransformation of T2 and HT2 toxin in cultured organs of Triticum durum Desf

The present study aimed at elucidating the uptake and biotransformation of T2 and HT2 toxins in five cultivars of durum wheat, by means of cultured plant organs. An almost complete absorption of T2 toxin (up to 100 µg) was noticed after 7 days, along with the contemporaneous formation of HT2 in planta, whereas HT2 showed a slower uptake by uninfected plant organs. Untargeted MS-analysis allowed to identify a large spectrum of phase I and phase II metabolites, resulting in 26 T2 and 23 HT2 metabolites plus tentative isomers. A novel masked mycotoxin, 3-acetyl-HT2-glucoside, was reported for the first time in wheat. The in vitro approach confirmed its potential to both investigate the contribution of plant metabolism in the biosynthesis of masked mycotoxins and to foresee the development of biocatalytic tools to develop nature-like mixtures to be used as reference materials.

Seasonal dynamics and spatial distribution of main Grapevine viruses in field-grown grapevine cultivars

Propagation of uninfected plant material is one of the most effective ways for controlling grapevine disease. Different diagnostic methods are available for testing viral infections, including serological techniques such as enzyme-linked immunosorbent assay (ELISA) and molecular techniques based on reverse transcription polymerase chain reaction (RT-PCR) and reverse transcription quantitative PCR (RT-qPCR). The objective of this study was to examine seasonal dynamics and spatial distribution of grapevine viruses within field-grown grapevine cultivars, in order to make more efficient virus detection by ELISA and RT-PCR, by identifying and selecting proper plant material and sampling time. For this purpose, a systematic investigation, considering different plant tissues and phenological stages, has been carried out through a multi-year study. Eight grapevine plants with single or multiple viral infections were selected and their state of infection was firstly monitored during the 2007 growing season, followed by a final infection assessment occurred after 5 years. Our results confirmed a strong erratic distribution of viruses within the vines, regardless of sampling stages, tissue type and/or different plant parts. For what concerns seasonal dynamics, our results on long-term infected grapevine plants corroborated the hypothesis that viruses behave differently from each other with respect to their irregular or rather homogeneous spatial distribution. Thus, an accurate sanitary status check of any grapevine must provide several random samples from different plant parts that have to be carried out several times both during a single growing season and through the years, removing infected vines, and taking vector populations under control.

Ecological and Evolutionary Stabilities of Biotrophism, Necrotrophism, and Saprotrophism.

Fungi have multiple trophic behaviors, including biotrophism (parasitism on living hosts), necrotrophism (parasitism through killing host tissues), and saprotrophism (feeding on decaying organic matter). Historical classifications of plant pathogens are based on many different axes, including their trophic dependence on living and dead plants, their pathogenicity and mutualistic relationship to host plants, and their transmission pathways and infection mechanisms. Such diverse classifications sometimes conflict with each other. Clarifying the delineations among these groups would promote synthesis of fungal biology with current ecological and evolutionary concepts. To ask when biotrophic, necrotrophic, or saprotrophic fungi are maintained and favored by selection, we constructed an epidemiological model that describes the transitions between four states of host plants: susceptible living plant (S), infected living plant (I), uninfected dead plant (D), and infected dead plant, or plant residue (R). States S and D represent two kinds of resource-living and dead plant tissues-for fungal inocula (I and R). We obtained values for the basic reproductive number (R0), which defines the persistence criteria of fungi. On the basis of our results, we propose four types of ecological groups, corresponding to the patterns of dependence on nutrient resources: (1) parasitism-dependent fungi, characterized by their critical dependence on living plants; (2) saprotrophism-dependent fungi, characterized by their critical dependence on dead plants; (3) facultatively dependent fungi, which are neither parasitism nor saprotrophism dependent; and (4) doubly dependent fungi, which are neither wholly parasitism dependent nor wholly saprotrophism dependent. This grouping can be used to suggest principles for effective pest control. Our model also reveals simple conditions for the evolution of fungal trophic behaviors. We found that, in the absence of a trade-off between virulence and other life-history parameters, milder fungal virulence in living plants is always selected for if plant-fungus population dynamics are stable. However, with sufficiently strong necrotrophic transmission, the host population densities show sustained cycles, which promote the evolution of higher virulence. Epidemiological synthesis of diverse trophism in plant-fungi relationship in our model thus opens the way to discuss the evolution of fungal lifestyles as a function of ecological conditions.

Corrigendum

EPPO BulletinVolume 49, Issue 1 p. 166-166 CorrigendumFree Access Corrigendum This article corrects the following: PM 7/127 (1) Acidovorax citrulli Volume 46Issue 3EPPO Bulletin pages: 444-462 First Published online: November 28, 2016 First published: 24 April 2019 https://doi.org/10.1111/epp.12569AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Corrigendum PM 7/127 (1) Acidovorax citrulli For the Diagnostic Standard PM 7/127 (1) Acidovorax citrulli, the EPPO Secretariat would like to make a correction to the section on the controls in Appendix 3 – PCR on plant extracts from symptomatic material or pure cultures (Schaad et al., 2000). The Negative isolation control (NIC) was incorrectly named Negative internal control (NIC). The Positive isolation control (PIC) was incorrectly named Positive internal control (PIC). The following 2 bullet points should therefore be replaced Old version Negative internal control (NIC) to monitor contamination during nucleic acid extraction: nucleic acid extraction and subsequent amplification, preferably of a sample of uninfected cucurbit plant matrix or, if not available, clean extraction buffer. Positive internal control (PIC) to ensure that nucleic acid of sufficient quantity and quality is isolated: nucleic acid extraction and subsequent amplification of the target organism or a cucurbit plant matrix sample containing the target organism (e.g. naturally infected host tissue or host tissue spiked with the target organism). Should be replaced by Corrected version Negative isolation control (NIC) to monitor contamination during nucleic acid extraction: nucleic acid extraction and subsequent amplification, preferably of a sample of uninfected cucurbit plant matrix or, if not available, clean extraction buffer. Positive isolation control (PIC) to ensure that nucleic acid of sufficient quantity and quality is isolated: nucleic acid extraction and subsequent amplification of the target organism or a cucurbit plant matrix sample containing the target organism (e.g. naturally infected host tissue or host tissue spiked with the target organism). The EPPO Secretariat apologies for any confusion this may have caused. Reference EPPO (2016) PM 7/127 (1) Acidovorax citrulli. Bulletin OEPP/EPPO Bulletin 46, 444– 462. Volume49, Issue1April 2019Pages 166-166 ReferencesRelatedInformation

Accumulation of salicylic acid in tomato plant under biological stress affects oviposition preference of Bemisia tabaci

ABSTRACT In field, plants are exposed to multiple biological stresses simultaneously; for example, insect damage and pathogenic virus infection. In this study, we constructed a simple tripartite experimental system using tomato plant, their insect pest Bemisia tabaci (whitefly), and infectious tomato mosaic virus (ToMV). In the choice test, whiteflies laid more eggs on uninfected plant than on ToMV-infected plant. Further, whiteflies hatched more and grew better on the uninfected plant. Salicylic acid (SA) accumulated in infected plants, and the expression of genes involved in SA production and SA-related response was significantly induced. These plant responses against ToMV infection were similar to those against whitefly attack or SA-treated plants. To examine the importance of plant endogenous SA for whitefly preference, we repeated the choice test using the NahG transgenic tomato that cannot accumulate SA. Whiteflies did not show oviposition preference between NahG plants with and without ToMV infection or whitefly infestation. Overall, whiteflies prefer healthy plants, and SA accumulation in response to biological stresses is involved in their preference.

Salicylic acid in Populus tomentosa is a remote signalling molecule induced by Botryosphaeria dothidea infection

The salicylic acid (SA) plays a critical role during the establishment of systemic acquired resistance (SAR) in uninfected plant tissues after localised exposure to a pathogen. Here, we studied SA in Populus tomentosa infected by the plant pathogen Botryosphaeria dothidea. The accumulation of SA and methyl salicylate (MeSA) occurred in chronological order in P. tomentosa. The SA and MeSA contents were greater at infected than uninfected sites. Additionally, a gene expression analysis indicated that SA might be accumulated by phenylalanine ammonialyase (PAL) and converted to MeSA by SA carboxyl methyltransferase (SAMT), while MeSA might convert to SA by SA-binding protein 2 (SABP2). The expressions of SAMT at infected sites and SABP2 at uninfected sites, respectively, were significantly up-regulated. Thus, SA might be converted to MeSA at infected sites and transported as a signalling molecule to uninfected sites, where it is converted to SA for SAR. Moreover, the expressions of pathogenesis-related genes PR-1, PR-2 and PR-5 in P. tomentosa were up-regulated by the B. dothidea infection. Our study determined that variations in SA and MeSA contents occur at infected and uninfected sites in poplar after pathogen infection and contributed to the remote signals for poplar SAR.

The effect of strawberry cultivars, infested with Tetranychus urticae (Acari: Tetranychidae), on the olfactory response of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

Tetranychus urticae Koch (Acari: Tetranychidae) is a key pest of agricultural crop. One of the best candidates for biological control of this mite is Neoseiulus californicus (McGregor) (Acari: Phytoseiidae). In this study, the olfactory response of the predatory mite to seven strawberry cultivars (‘Marak’, ‘Yalova’, ‘Aliso’, ‘Gaviota’, ‘Sequoia’, ‘Camarosa’ and ‘Chandler’) was studied using a Y-tube olfactometer. We used two-day-old female predatory mites that were reared on spider mite-infested strawberry. The behavioral response of the predator was studied in four experiments: 1) clean air vs. uninfected strawberry plant, 2) clean air vs. spider mite-infested strawberry plant, 3) uninfected strawberry plant vs. spider mite-infested strawberry plant and 4) two-cultivar choice test (spider mite-infested). In the first experiment, the attraction of the predatory mite to uninfected strawberry plant volatiles was significant. In the second test, the predators significantly preferred volatiles from strawberry plant infested with T. urticae to clean air. In the third test, 68% to 80% of the predatory mites were attracted to spider mite-infested strawberry plant volatiles compared with uninfected plants. Among the seven strawberry cultivars, the predator responses to volatiles of infested plants varied 62% to 83% and to volatiles of uninfested plant varied 59% to 75%. Herbivore – induced plant volatile emitted from strawberry infested with T. urticae attract the predatory mite. The last test showed that ‘Aliso’ and ‘Chandler’ were more attractive for the predatory mite.

Plant organ cultures as masked mycotoxin biofactories: Deciphering the fate of zearalenone in micropropagated durum wheat roots and leaves.

“Masked mycotoxins” senso strictu are conjugates of mycotoxins resulting from metabolic pathways activated by the interplay between pathogenic fungi and infected plants. Zearalenone, an estrogenic mycotoxin produced by Fusarium spp, was the first masked mycotoxin ever described in the literature, but its biotransformation has been studied to a lesser extent if compared to other compounds such as deoxynivalenol. We presented herein the first application of organ and tissue culture techniques to study the metabolic fate of zearalenone in durum wheat, using an untargeted HR-LCMS approach. A complete, quick absorption of zearalenone by uninfected plant organs was noticed, and its biotransformation into a large spectrum of phase I and phase II metabolites has been depicted. Therefore, wheat organ tissue cultures can be effectively used as a biocatalytic tool for the production of masked mycotoxins, as well as a replicable model for the investigation of the interplay between mycotoxins and wheat physiology.

Phytopathogenic fungus hosts a plant virus: A naturally occurring cross-kingdom viral infection

The transmission of viral infections between plant and fungal hosts has been suspected to occur, based on phylogenetic and other findings, but has not been directly observed in nature. Here, we report the discovery of a natural infection of the phytopathogenic fungus Rhizoctonia solani by a plant virus, cucumber mosaic virus (CMV). The CMV-infected R. solani strain was obtained from a potato plant growing in Inner Mongolia Province of China, and CMV infection was stable when this fungal strain was cultured in the laboratory. CMV was horizontally transmitted through hyphal anastomosis but not vertically through basidiospores. By inoculation via protoplast transfection with virions, a reference isolate of CMV replicated in R. solani and another phytopathogenic fungus, suggesting that some fungi can serve as alternative hosts to CMV. Importantly, in fungal inoculation experiments under laboratory conditions, R. solani could acquire CMV from an infected plant, as well as transmit the virus to an uninfected plant. This study presents evidence of the transfer of a virus between plant and fungus, and it further expands our understanding of plant-fungus interactions and the spread of plant viruses.

Identification and Symbiotic Phenotype Characterization of an OPDA Reductase Gene AsOPR1 in Chinese Milk Vetch

In higher plants, the 12-oxo-phytodienoic acid reductase (OPR) family mainly consists of two subgroups. OPR3-like enzymes belong to subgroup II, and they were proved to be key functional enzymes participating in jasmonic acid (JA) biosynthesis, while functions of OPR1-like enzymes classified into subgroup I remain largely unclear, particularly in symbiosis. This study identified and functionally characterized a gene encoding 12-oxophytodienoate reductase in Astragalus sinicus. Sequence homology analysis indicated that this gene encodes an OPR1-like enzyme. It was found that the gene expression of AsOPR1 was upregulated after inoculation with Mesorhizobium huakuii 7653R. Subcellular localization showed that in uninfected host plant cells, AsOPR1 was localized in the amyloplast, a differentiated form of plastid; while in the infected cells, AsOPR1 co-localized with rhizobia. Knockdown of the AsOPR1 gene decreased the nodule number to 34.6% that of the control roots, and significantly reduced the JA level in both transgenic roots and nodules, while overexpression of the AsOPR1 gene resulted in enlarged nodule meristem, but caused no changes in nodule number. Taken together, these results indicate that AsOPR1 may participate in the regulation of nodule formation and development, as well as affect endogenous JA metabolism.

Photosynthetic responses to phytoplasma infection in Chinese jujube

Phytoplasma is one of the most devastating plant pathogens. Jujube witches' broom (JWB) is a typical and highly fatal phytoplasma disease of Chinese jujube (Ziziphus jujuba Mill.), which is widely cultivated in Asia. To further elucidate the mechanism of plant-phytoplasma interaction, we first compared the effects of phytoplasma infection on photosynthetic pigments and activities between a JWB-resistant cultivar (Xingguang) and a susceptible cultivar (Pozao). Total chlorophyll and carotenoid levels were significantly decreased in the susceptible cultivar at later stages of infection, but were remarkably increased in the resistant cultivar at the earlier stages. Compared to uninfected plant, a significant decrease in the main photochemical parameters (Fv/Fm, ΦPSII and qP) was recorded at the initial stages of infection in the resistant cultivar, but occurred at later stages in the susceptible cultivar. Meanwhile, the qRT-PCR results of four key photosynthesis-related genes (ZjGluTR, ZjCBP, ZjRubisco and ZjRCA2) demonstrated that the expression patterns were similar in uninfected cultivars, but up-regulated in resistant cultivar and down-regulated in the susceptible one at 12 wks after grafting inoculation. Collectively, our data indicated that the resistant cultivar ‘Xingguang’ undergoes a decrease in initial stage (inhibiting phytoplasma multiplication) and then a rapid enhancement of photosynthetic activity (helping jujube recovery) in response to phytoplasma infection, while the susceptible cultivar ‘Pozao’ displays a later decrease in photosynthetic activity. The novel photosynthetic response pattern of the resistant cultivar may contribute to its stronger immunity to phytoplasma infection, which provides new insights into plant-phytoplasma interactions.

Transcriptome Analysis of an Anthracnose-Resistant Tea Plant Cultivar Reveals Genes Associated with Resistance to Colletotrichum camelliae.

Tea plant breeding is a topic of great economic importance. However, disease remains a major cause of yield and quality losses. In this study, an anthracnose-resistant cultivar, ZC108, was developed. An infection assay revealed different responses to Colletotrichum sp. infection between ZC108 and its parent cultivar LJ43. ZC108 had greater resistance than LJ43 to Colletotrichum camelliae. Additionally, ZC108 exhibited earlier sprouting in the spring, as well as different leaf shape and plant architecture. Microarray data revealed that the genes that are differentially expressed between LJ43 and ZC108 mapped to secondary metabolism-related pathways, including phenylpropanoid biosynthesis, phenylalanine metabolism, and flavonoid biosynthesis pathways. In addition, genes involved in plant hormone biosynthesis and signaling as well as plant-pathogen interaction pathways were also changed. Quantitative real-time PCR was used to examine the expression of 27 selected genes in infected and uninfected tea plant leaves. Genes encoding a MADS-box transcription factor, NBS-LRR disease-resistance protein, and phenylpropanoid metabolism pathway components (CAD, CCR, POD, beta-glucosidase, ALDH and PAL) were among those differentially expressed in ZC108.