Proteomic analysis of rice defense response induced by probenazole

Two thiadiazole compounds promote rice defence against Xanthomonas oryzae pv. oryzae by suppressing the bacterium's production of extracellular polysaccharides

Thiazole, isothiazole, thiadiazole, and their derivatives are used to control various human, animal and plant diseases. In addition to having direct anti-microbial and anti-fungal properties, these compounds are thought to induce host defences, but the mechanism of defence induction remains poorly understood. This article reports that the thiadiazoles of zinc thiazole and bismerthiazol induce H2 O2 accumulation, up-regulation of defence-related genes, callose deposition and hypersensitive response-like cell death in rice leaves infected with Xanthomonas oryaze pv. oryzae (Xoo) strain ZJ173, but not in non-infected leaves. These defence responses in Xoo-infected leaves were suppressed by the exogenous application of catalase, which reduces H2 O2 accumulation. The application of extracellular polysaccharides (EPSs) extracted from strain ZJ173 significantly compromised rice defence against ZJ173 with or without thiadiazole treatment. The EPS-deficient Xoo mutant ∆gumH triggered a stronger defence than its parent strain ZJ173. The thiadiazole treatments reduced EPS production by strain ZJ173, but not by the thiadiazole-resistant strain 2-1-1, which is thiadiazole resistant in vivo, but not in vitro; moreover, enhanced defence was not detected in thiadiazole-treated rice inoculated with 2-1-1. Based on these data, we infer that zinc thiazole and bismerthiazol promote rice defence against Xoo by inhibiting the production of bacterial EPS.

Comparative proteomics reveals differential induction of both biotic and abiotic stress response associated proteins in rice during Xanthomonas oryzae pv. oryzae infection

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight disease in rice and brutally affects the yield up to 50 % of total production. Here, we report a comparative proteomics analysis of total foliar protein isolated from infected rice leaves of susceptible Pusa Basmati 1 (PB1) and resistant Oryza longistaminata genotypes. Two-dimensional gel electrophoresis (2-DE) coupled with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) approaches identified 29 protein spots encoding unique proteins from both the genotypes. Identified proteins belonged to a large number of biological and molecular functions related to biotic and abiotic stress proteins which are potentially involved during Xoo infection. Biotic and abiotic stress-related proteins were induced during Xoo infection, indicating the activation of common stress pathway during bacterial blight infection. Candidate genes conferring tolerance against bacterial blight, which include germin-like protein, putative r40c1, cyclin-dependent kinase C, Ent-isokaur-15-ene synthase and glutathione-dependent dehydroascorbate reductase 1 (GSH-DHAR1), were also induced, with germin-like proteins induced only in the resistant rice genotype O. longistaminata. Energy, metabolism and hypothetical proteins were common among both the genotypes. Further, host defence/stress-related proteins were mostly expressed in resistant genotype O. longistaminata, indicating possible co-evolution of the pathogen and the wild rice, O. longistaminata.

Proteomic analysis of 'Zaosu' pear (Pyrus bretschneideri Rehd.) and its red skin bud mutation

BACKGROUND

Breeding for strong red skin color is an important objective of the pear breeding program. There are few reports of proteome research in green skin pear and its red skin bud mutation. The manuscript at hand is one of the first studies dealing with 2D-PAGE-based analysis of pear fruits and leaves, establishing a suitable sample preparation and testing different 2D-PAGE protocols. Therefore, it may grant a basis for further studies on the pear proteome being the studies main goal. A proteomic analysis was conducted on leaves and fruits of 'Zaosu' pear (Pyrus bretschneideri Rehd.) and its red skin bud mutation in order to reveal their genetic differences in the protein level.

RESULTS

In the present study, the optimized two-dimensional (2-D) gel electrophoresis system of pear leaf and fruit was set up, and applied to analyze the leaves and fruit protein. The interesting peptide fragments were determined using 4800 Plus MALDI TOF/TOFTM Analyzer mass spectrometer, and the sequence obtained was blasted in NCBInr to identify the differentially-expressed protein. In the 1.5-fold differently-expressed proteins between 'Zaosu' pear and its mutant, 10 out of 35 proteins in fruit and 12 out of 24 ones in leaves were identified successfully. Among the 22 identified proteins, 7 protein spots were related to photosynthesis and energy metabolism; 4 were associated with environmental stress; 4 with disease defense; 2 with amino acid metabolism; 2 with cytoskeleton; 1 with antioxidant function; 1 with calcium metabolism; and 1 with unknown function. Moreover, related physiological index, such as chlorophyll content, Rubisco content and polyphone oxidase activity, were different between 'Zaosu' pear and its mutant.

CONCLUSION

A 2-D gel electrophoresis system of pear leaves and fruits was established, which was suitable for the analysis of proteome comparison. To the best of our knowledge, we have performed the first analysis of the proteomic changes in leaves and fruits of 'Zaosu' pear and its red skin bud mutation. Our study provides important information on the use of proteomic methods for studying protein regulation of 'Zaosu' pear and its red skin bud mutation.

Proteomic analysis of soybean defense response induced by cotton worm (prodenia litura, fabricius) feeding

BACKGROUND

Cotton worm is one of the main insects of soybean in southern China. Plants may acquire defense mechanisms that confer protection from predation by herbivores. Induced responses can lead to increased resistance against herbivores in many species. This study focuses on searching changed proteins in soybean defense response induced by cotton worm feeding.

RESULTS

Ten protein spots that are changed in abundance in response to cotton worm feeding were identified by Two-dimensional gel electrophoresis (2-DE). A total of 11 unique proteins from these spots were identified by MALDI-TOF MS. The mRNA and protein relative expression levels of most changed proteins were up-regulated. These proteins were mainly involved in physiological processes, including active oxygen removal, defense signal transduction, and metabolism regulation.

CONCLUSION

This is the first proteomic analysis of the soybean defense response induced by cotton worm. The differentially expressed proteins could work together to play a major role in the induced defense response. PAL and SAMS were up-regulated at both the protein and mRNA levels. These genes can be strongest candidates for further functional research.

Proteomic response of wheat embryos to fosthiazate stress in a protected vegetable soil

A proteomic analysis of wheat defense response induced by the widely used organophosphorus nematicide fosthiazate is reported. Seed germination and two-dimensional gel electrophoresis (2-DE) experiments were performed using a Chinese wheat cultivar, Zhenmai No. 5. Root and shoot elongation decreased but thiobarbituric acid reactive substances (TBARS) content in embryos increased with increasing pesticide concentration. More than 1000 protein spots were reproducibly detected in each silver-stained gel. Thirty-seven protein spots with at least 2-fold changes were identified using MALDI-TOF MS/MS analysis. Of these, 24 spots were up-regulated and 13 were down-regulated. Proteins identified included some well-known classical stress responsive proteins under abiotic or biotic stresses as well as some unusual responsive proteins. Ten responsive proteins were reported for the first time at the proteomic level, including fatty acyl CoA reductase, dihydrodipicolinate synthase, DEAD-box ATPase-RNA-helicase, fimbriata-like protein, waxy B1, rust resistance kinase Lr10, putative In2.1 protein, retinoblastoma-related protein 1, pollen allergen-like protein and S-adenosyl-L-methionine:phosphoethanolamine N-methyltransferase. The proteins identified were involved in several processes such as metabolism, defense/detoxification, cell structure/cell growth, signal transduction/transcription, photosynthesis and energy. Seven candidate proteins were further analyzed at the mRNA level by RT-PCR to compare transcript and protein accumulation patterns, revealing that not all the genes were correlated well with the protein level. Identification of these responsive proteins may provide new insight into the molecular basis of the fosthiazate-stress response in the early developmental stages of plants and may be useful in stress monitoring or stress-tolerant crop breeding for environmentally friendly agricultural production.

Application of proteomics to investigate stress-induced proteins for improvement in crop protection

Proteomics has contributed to defining the specific functions of genes and proteins involved in plant-pathogen interactions. Proteomic studies have led to the identification of many pathogenicity and defense-related genes and proteins expressed during phytopathogen infections, resulting in the collection of an enormous amount of data. However, the molecular basis of plant-pathogen interactions remains an intensely active area of investigation. In this review, the role of differential analysis of proteins expressed during fungal, bacterial, and viral infection is discussed, as well as the role of JA and SA in the production of stress related proteins. Resistance acquired upon induction of stress related proteins in intact plant leaves is mediated by potentiation of pathogens via signal elicitors. Stress related genes extensively used in biotechnology had been cited. Stress related proteins identified must be followed through for studying the molecular mechanism for plant defense against pathogens.

Metabolomic and transcriptomic analysis of the rice response to the bacterial blight pathogen Xanthomonas oryzae pv. oryzae

Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae (Xoo), gives rise to devastating crop losses in rice. Disease resistant rice cultivars are the most economical way to combat the disease. The TP309 cultivar is susceptible to infection by Xoo strain PXO99. A transgenic variety, TP309_Xa21, expresses the pattern recognition receptor Xa21, and is resistant. PXO99 big up tri, openraxST, a strain lacking the raxST gene, is able to overcome Xa21-mediated immunity. We used a single extraction solvent to demonstrate comprehensive metabolomics and transcriptomics profiling under sample limited conditions, and analyze the molecular responses of two rice lines challenged with either PXO99 or PXO99 big up tri, openraxST. LC-TOF raw data file filtering resulted in better within group reproducibility of replicate samples for statistical analyses. Accurate mass match compound identification with molecular formula generation (MFG) ranking of 355 masses was achieved with the METLIN database. GC-TOF analysis yielded an additional 441 compounds after BinBase database processing, of which 154 were structurally identified by retention index/MS library matching. Multivariate statistics revealed that the susceptible and resistant genotypes possess distinct profiles. Although few mRNA and metabolite differences were detected in PXO99 challenged TP309 compared to mock, many differential changes occurred in the Xa21-mediated response to PXO99 and PXO99 big up tri, openraxST. Acetophenone, xanthophylls, fatty acids, alkaloids, glutathione, carbohydrate and lipid biosynthetic pathways were affected. Significant transcriptional induction of several pathogenesis related genes in Xa21 challenged strains, as well as differential changes to GAD, PAL, ICL1 and Glutathione-S-transferase transcripts indicated limited correlation with metabolite changes under single time point global profiling conditions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-010-0218-7) contains supplementary material, which is available to authorized users.

Genome-wide analysis of genes targeted by qLTG3-1 controlling low-temperature germinability in rice

The control of seed germination under environmental conditions, where plants will be grown, is important for the adaptability of plants. Low-temperature is one of the most common environmental stress factors that affect plant growth and development and places a major limit on crop productivity in cultivated areas. Previously, qLTG3-1, a major quantitative trait locus controlling low-temperature tolerance at the germination stage in rice (called low-temperature germinability) was identified, which encodes a protein of unknown function. To identify genes targeted by qLTG3-1, a genome-wide expression profiling analysis using the 44 K Rice Oligo microarray was performed. Because the expression of qLTG3-1 was dramatically increased at 1 day after incubation, the expression profiles at this time were compared between Hayamasari, which has a loss-of-function qLTG3-1 allele, and a near isogenic line with a functional allele. A total of 4,587 genes showed significant differences between their expression levels in the two lines. Most of these genes might be involved in the process of seed germination itself, and then a focus was made on qLTG3-1 dependently induced or suppressed genes, defined as 'qLTG3-1 dependent' genes. Twenty-nine 'qLTG3-1 dependent' genes with diverse functions were categorized, implying that disruption of cellular homeostasis leads to a wide range of metabolic alterations and diverse cross-talk between various signaling pathways. In particular, genes involved in defense responses were up-regulated by qLTG3-1, indicating that qLTG3-1 expression is required for the expression of defense response genes in low-temperature germinability in rice.

Rice proteomics: ending phase I and the beginning of phase II

Rice is a critically important food crop plant on our planet. It is also an excellent model plant for cereal crops, and now in position to serve as a reference plant for biofuel production. Proteomics study of rice therefore is crucial to better understand "rice" as a whole. Rice proteomics has moved well beyond the initial proteome analysis in the early to late 1990s. Since the year 2000, numerous proteomic studies have been performed in rice during growth and development and against a wide variety of environmental factors. These proteomic investigations have established the high-resolution 2-D reference gels of rice tissues, organs, and organelle under normal and adverse (stressed) conditions by optimizing suitable, reproducible systems for gel, and MS-based proteomic techniques, which "rejuvenated" the rice proteome field. This constituted the "phase I" in rice proteomics, and resulted in rice being labeled as the "cornerstone" of cereal food crop proteomes. Now, we are in position to state that rice proteomics today marks the "beginning of phase II". This is due to the fact that rice researchers are capable of digging deeper into the rice proteome, mapping PTMs (in particular reversible protein phosphorylation), performing inter- and intra-species comparisons, integrating proteomics data with other "omic" technologies-generated data, and probing the functional aspect of individual proteins. These advancements and their impact on the future of rice proteomics are the focus of this review.

Small heat-shock protein HspL is induced by VirB protein(s) and promotes VirB/D4-mediated DNA transfer in Agrobacterium tumefaciens

Agrobacterium tumefaciens is a Gram-negative plant-pathogenic bacterium that causes crown gall disease by transferring and integrating its transferred DNA (T-DNA) into the host genome. We characterized the chromosomally encoded alpha-crystallin-type small heat-shock protein (alpha-Hsp) HspL, which was induced by the virulence (vir) gene inducer acetosyringone (AS). The transcription of hspL but not three other alpha-Hsp genes (hspC, hspAT1, hspAT2) was upregulated by AS. Further expression analysis in various vir mutants suggested that AS-induced hspL transcription is not directly activated by the VirG response regulator but rather depends on the expression of VirG-activated virB genes encoding components of the type IV secretion system (T4SS). Among the 11 virB genes encoded by the virB operon, HspL protein levels were reduced in strains with deletions of virB6, virB8 or virB11. VirB protein accumulation but not virB transcription levels were reduced in an hspL deletion mutant early after AS induction, implying that HspL may affect the stability of individual VirB proteins or of the T4S complex directly or indirectly. Tumorigenesis efficiency and the VirB/D4-mediated conjugal transfer of an IncQ plasmid RSF1010 derivative between A. tumefaciens strains were reduced in the absence of HspL. In conclusion, increased HspL abundance is triggered in response to certain VirB protein(s) and plays a role in optimal VirB protein accumulation, VirB/D4-mediated DNA transfer and tumorigenesis.