Rice (Oryza sativa L.) is a staple food crop, feeding more than 50% of the world's population. Diseases caused by bacterial, fungal, and viral pathogens constantly threaten the rice production and lead to enormous yield losses. Bacterial blight (BB) and bacterial leaf streak (BLS), caused respectively by gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), are two important diseases affecting rice production worldwide. Due to the economic importance, extensive genetic and genomic studies have been conducted to elucidate the molecular mechanism of rice response to Xoo and Xoc in the last two decades. A series of resistance (R) genes and their cognate avirulence and virulence effector genes have been characterized. Here, we summarize the recent advances in studies on interactions between rice and the two pathogens through these R genes or their products and effectors. Breeding strategies to develop varieties with durable and broad-spectrum resistance to Xanthomonas oryzae based on the published studies are also discussed.

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Posttranslational lipid modifications are important for proper localization of many proteins in eukaryotic cells. However, the functional interrelationships between lipid modification processes in plants remain unclear. Here we demonstrate that the two heterotrimeric G-protein g-subunits from Arabidopsis (Arabidopsis thaliana), AGG1 and AGG2, are prenylated, and AGG2 is S-acylated. In wild type, enhanced yellow fluorescent protein-fused AGG1 and AGG2 are associated with plasma membranes, with AGG1 associated with internal membranes as well. Both can be prenylated by either protein geranylgeranyltransferase I (PGGT-I) or protein farnesyltransferase (PFT). Their membrane localization is intact in mutants lacking PFT activity and largely intact in mutants lacking PGGT-I activity but is disrupted in mutants lacking both PFT and PGGT-I activity. Unlike in mammals, Arabidopsis Ggs do not rely on functional Ga for membrane targeting. Mutation of the sixth to last cysteine, the putative S-acylation acceptor site, causes a dramatic change in AGG2 but not AGG1 localization pattern, suggesting S-acylation serves as an important additional signal for AGG2 to be targeted to the plasma membrane. Domain-swapping experiments suggest that a short charged sequence at the AGG2 C terminus contributes to AGG2's efficient membrane targeting compared to AGG1. Our data show the large degree to which PFT and PGGT-I can compensate for each other in plants and suggest that differential lipid modification plays an important regulatory role in plant protein localization.

(Q.Z., M.P.R.)Arabidopsis (Arabidopsis thaliana) mutants lacking a functional ERA1 gene, which encodes the b-subunit of protein farnesyltransferase (PFT), exhibit pleiotropic effects that establish roles for protein prenylation in abscisic acid (ABA) signaling and meristem development. Here, we report the effects of T-DNA insertion mutations in the Arabidopsis GGB gene, which encodes the b-subunit of protein geranylgeranyltransferase type I (PGGT I). Stomatal apertures of ggb plants were smaller than those of wild-type plants at all concentrations of ABA tested, suggesting that PGGT I negatively regulates ABA signaling in guard cells. However, germination of ggb seeds in response to ABA was similar to the wild type. Lateral root formation in response to exogenous auxin was increased in ggb seedlings compared to the wild type, but no change in auxin inhibition of primary root growth was observed, suggesting that PGGT I is specifically involved in negative regulation of auxin-induced lateral root initiation. Unlike era1 mutants, ggb mutants exhibited no obvious developmental phenotypes. However, era1 ggb double mutants exhibited more severe developmental phenotypes than era1 mutants and were indistinguishable from plp mutants lacking the shared a-subunit of PFT and PGGT I. Furthermore, overexpression of GGB in transgenic era1 plants partially suppressed the era1 phenotype, suggesting that the relatively weak phenotype of era1 plants is due to partial redundancy between PFT and PGGT I. These results are discussed in the context of Arabidopsis proteins that are putative substrates of PGGT I.Protein prenylation involves the formation of a thioether bond between a farnesyl (C15) or geranylgeranyl (C20) group and a C-terminal Cys residue (Clarke, 1992;Zhang and Casey, 1996). This posttranslational modification promotes protein-membrane and, in many cases, protein-protein interactions. Three protein prenyltransferases are known to catalyze protein prenylation in plants and other eukaryotes: (1) a heterodimeric protein farnesyltransferase (PFT) that consists of a-and b-subunits and transfers a farnesyl group from farnesyl pyrophosphate (FPP) to proteins bearing a C-terminal CaaX motif, where ''C'' is Cys, ''a'' is often an aliphatic amino acid, and ''X'' is generally Met, Ala, Gln, Ser, or Cys; (2) a heterodimeric type I protein geranylgeranyltransferase (PGGT I) that shares a common a-subunit with PFT but possesses a distinct b-subunit and transfers a geranylgeranyl group from geranylgeranyl pyrophosphate (GGPP) to proteins bearing a C-terminal CaaX motif, where ''X'' is Leu; and (3) a heterotrimeric type II protein geranylgeranyltransferase (PGGT II or Rab PGGT) that consists of distinct a-and b-subunits, as well as a third subunit called the Rab escort protein, and transfers a geranylgeranyl group from GGPP to Rab protein substrates (Clarke, 1992;Zhang and Casey, 1996;Crowell, 2000). PFT subunits have been identified and characterized from pea (Pisum sativum; Yang et al., 1993;Qian et al., 1996), tomato (Lycopersicon ...

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BackgroundPreserving the integrity of the blood-brain barrier (BBB) is beneficial to avoid further brain damage after acute ischemic stroke (AIS). Astrocytes, an important component of the BBB, promote BBB breakdown in subjects with AIS by secreting inflammatory factors. The glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 (Ex-4) protects the BBB and reduces brain inflammation from cerebral ischemia, and GLP-1R is expressed on astrocytes. However, the effect of Ex-4 on astrocytes in subjects with AIS remains unclear.MethodsIn the present study, we investigated the effect of Ex-4 on astrocytes cultured under oxygen-glucose deprivation (OGD) plus reoxygenation conditions and determined whether the effect influences bEnd.3 cells. We used various methods, including permeability assays, western blotting, immunofluorescence staining, and gelatin zymography, in vitro and in vivo.ResultsEx-4 reduced OGD-induced astrocyte-derived vascular endothelial growth factor (VEGF-A), matrix metalloproteinase-9 (MMP-9), chemokine monocyte chemoattractant protein-1 (MCP-1), and chemokine C-X-C motif ligand 1 (CXCL-1). The reduction in astrocyte-derived VEGF-A and MMP-9 was related to the increased expression of tight junction proteins (TJPs) in bEnd.3 cells. Ex-4 improved neurologic deficit scores, reduced the infarct area, and ameliorated BBB breakdown as well as decreased astrocyte-derived VEGF-A, MMP-9, CXCL-1, and MCP-1 levels in ischemic brain tissues from rats subjected to middle cerebral artery occlusion. Ex-4 reduced the activation of the JAK2/STAT3 signaling pathway in astrocytes following OGD.ConclusionBased on these findings, ischemia-induced inflammation and BBB breakdown can be improved by Ex-4 through an astrocyte-dependent manner.

Tortula ruralis (Syntrichia ruralis) is a useful model system for the study of gene control in response to severe water deficit-stress. EST gene discovery efforts utilizing desiccated gametophytes have identified two cDNAs designated Elipa and Elipb with significant similarity to early light-inducible proteins (ELIPs). Elipa is 1006 bp in length, encoding a 212 amino acid deduced polypeptide (ELIPa) with a predicted molecular mass of 23.3 kDa and pI of 5.57. Elipb is 997 bp in length, encoding a 224 amino acid deduced polypeptide (ELIPb) with a predicted molecular mass of 24.4 kDa and pI of 9.27. Phylogenetic analysis demonstrated that ELIPa and ELIPb are reproducibly grouped with ELIP sequences derived from desiccation-tolerance tissues. RNA blot hybridization was used to analyse Elipa and Elipb mRNA abundance in response to a variety of stresses. Elipa steady-state transcript levels increased in response to slow desiccation, rapid desiccation/rehydration, salinity, ABA, and rehydration in high light. The Elipb transcript was only detectable in response to ABA or rehydration in high light. It is postulated that ELIPa and ELIPb are an adaptive response to stress-induced photodamage within the moss chloroplast, and play a key role in the protection and/or repair of the photosynthetic apparatus.

In this study, to systematically identify the most stably expressed genes for internal reference in zebrafish Danio rerio investigations, 37 D. rerio transcriptomic datasets (both RNA sequencing and microarray data) were collected from gene expression omnibus (GEO) database and unpublished data, and gene expression variations were analysed under three experimental conditions: tissue types, developmental stages and chemical treatments. Forty-four putative candidate genes were identified with the c.v. <0·2 from all datasets. Following clustering into different functional groups, 21 genes, in addition to four conventional housekeeping genes (eef1a1l1, b2m, hrpt1l and actb1), were selected from different functional groups for further quantitative real-time (qrt-)PCR validation using 25 RNA samples from different adult tissues, developmental stages and chemical treatments. The qrt-PCR data were then analysed using the statistical algorithm refFinder for gene expression stability. Several new candidate genes showed better expression stability than the conventional housekeeping genes in all three categories. It was found that sep15 and metap1 were the top two stable genes for tissue types, ube2a and tmem50a the top two for different developmental stages, and rpl13a and rp1p0 the top two for chemical treatments. Thus, based on the extensive transcriptomic analyses and qrt-PCR validation, these new reference genes are recommended for normalization of D. rerio qrt-PCR data respectively for the three different experimental conditions.