Background: A lesion-mimic mutant in rice (Oryza sativaL.),spotted leaf 5(spl5), displays a disease-resistance-enhanced phenotype, indicating that SPL5 negatively regulates cell death and resistance responses. To understand the molecular mechanisms ofSPL5mutation-induced cell death and resistance responses, a proteomics-based approach was used to identify differentially accumulated proteins between thespl5mutant and wild type (WT).Results: Proteomic data from two-dimensional gel electrophoresis showed that 14 candidate proteins were significantly up- or down-regulated in thespl5mutant compared with WT. These proteins are involved in diverse biological processes including pre-mRNA splicing, amino acid metabolism, photosynthesis, glycolysis, reactive oxygen species (ROS) metabolism, and defense responses. Two candidate proteins with a significant up-regulation inspl5– APX7, a key ROS metabolism enzyme and Chia2a, a pathogenesis-related protein – were further analyzed by qPCR and enzyme activity assays. Consistent with the proteomic results, both transcript levels and enzyme activities of APX7 and Chia2a were significantly induced during the course of lesion formation inspl5leaves.Conclusions: Many functional proteins involving various metabolisms were likely to be responsible for the lesion formation ofspl5mutant. Generally, inspl5, the up-regulated proteins involve in defense response or PCD, and the down-regulated ones involve in amino acid metabolism and photosynthesis. These results may help to gain new insight into the molecular mechanism underlyingspl5-induced cell death and disease resistance in plants.

Bacterial blight (BB) is a globally devastating rice disease caused by Xanthomonas oryzae pv. oryzae (Xoo). The use of disease resistance (R) genes in rice breeding is an effective and economical strategy for the control of this disease. Nevertheless, a majority of R genes lack durable resistance for long-term use under global warming conditions. Here, we report the isolation of a novel executor R gene, Xa7, that confers extremely durable, broad-spectrum, and heat-tolerant resistance to Xoo. The expression of Xa7 was induced by incompatible Xoo strains that secreted the transcription activator-like effector (TALE) AvrXa7 or PthXo3, which recognized effector binding elements (EBEs) in the Xa7 promoter. Furthermore, Xa7 induction was faster and stronger under high temperatures. Overexpression of Xa7 or co-transformation of Xa7 with avrXa7 triggered a hypersensitive response in plants. Constitutive expression of Xa7 activated a defense response in the absence of Xoo but inhibited the growth of transgenic rice plants. In addition, analysis of over 3000 rice varieties showed that the Xa7 locus was found primarily in the indica and aus subgroups. A variation consisting of an 11-bp insertion and a base substitution (G to T) was found in EBEAvrXa7 in the tested varieties, resulting in a loss of Xa7 BB resistance. Through a decade of effort, we have identified an important BB resistance gene and characterized its distinctive interaction with Xoo strains; these findings will greatly facilitate research on the molecular mechanism of Xa7-mediated resistance and promote the use of this valuable gene in breeding.

When the distance between the source and the target is long, the signal will be affected by atmospheric turbulence, weather conditions and obstacles, which cannot support the information transmission. One of the existing solutions is to use relay-assisted technology (RAT). It makes the communications between the source and the destination possible under better channel conditions by setting up relay between the source and the destination. There are few comprehensive articles about relay-assisted technology in OWC. To fill this gap, this paper introduces the RAT of indoor optical wireless communications (IOWC), outdoor optical wireless communications (OOWC) and underwater optical wireless communications (UOWC) in different application scenarios, which has a better effect than direct communication between source and destination. The relay protocols, channel models, modulation techniques under three relay modes are reviewed. Finally, challenges of RAT in OWC are put forward and potential solutions are also given.

Background: Rice mutant,spl5(spotted leaf 5), has spontaneous hypersensitive-like lesions on its leaves and shows enhanced resistance to pathogens, indicating thatSPL5plays a role in programmed cell death (PCD) and disease resistance. To understand the molecular mechanism ofSPL5gene, we investigated the transcriptome profiles of thespl5mutant leaves with few lesions (FL) and leaves with many lesions (ML) compared to the wild-type (WT) leaves respectively by microarray.Results: The data from microarray revealed that 243 and 896 candidate genes (Fold change ≥ 3.0) were up- or down-regulated in thespl5-FL andspl5-ML, respectively, and a large number of these genes involved in biotic defense responses or reactive oxygen species (ROS) metabolism. Interestingly, according to our microarray and real-time PCR assays, the expressions of a transcription factorOsWRKY14and genes responsible for the biosynthesis of serotonin, anthranilate synthase (AS), indole-3-glycerolphosphate synthase (IGPS), tryptophan synthase (TS) and tryptophan decarboxylase (TDC) were significantly up-regulated in thespl5mutant. It has been reported previously thatTSandTDCexpressions are regulated byOsWRKY14in rice, which raises the possibility thatOsWRKY14regulates serotonin production through the up-regulation ofTSandTDC. Our HPLC analysis further confirmed that serotonin levels were higher in the leaves ofspl5mutant than that in WT.Conclusions: Since the serotonin plays a critical role in inducing disease-resistance, the increased serotonin level may contribute, at least partly, to the disease resistance inspl5. TheSPL5gene may act as a negative regulatory factor activating the serotonin metabolic pathway, and these results might provide a new insight into thespl5-induced defense response mechanisms in plants.

Executor (E) genes comprise a new type of plant resistance (R) genes, identified from host–Xanthomonas interactions. The Xanthomonas-secreted transcription activation-like effectors (TALEs) usually function as major virulence factors, which activate the expression of the so-called “susceptibility” (S) genes for disease development. This activation is achieved via the binding of the TALEs to the effector-binding element (EBE) in the S gene promoter. However, host plants have evolved EBEs in the promoters of some otherwise silent R genes, whose expression directly causes a host cell death that is characterized by a hypersensitive response (HR). Such R genes are called E genes because they trap the pathogen TALEs in order to activate expression, and the resulting HR prevents pathogen growth and disease development. Currently, deploying E gene resistance is becoming a major component in disease resistance breeding, especially for rice bacterial blight resistance. Currently, the biochemical mechanisms, or the working pathways of the E proteins, are still fuzzy. There is no significant nucleotide sequence homology among E genes, although E proteins share some structural motifs that are probably associated with the signal transduction in the effector-triggered immunity. Here, we summarize the current knowledge regarding TALE-type avirulence proteins, E gene activation, the E protein structural traits, and the classification of E genes, in order to sharpen our understanding of the plant E genes.

The regulation of gene expression is crucial for biological plant growth and development, with transcription factors (TFs) serving as key switches in this regulatory mechanism. GOLDEN2-LIKE (GLK) TFs are a class of functionally partially redundant nuclear TFs belonging to the GARP superfamily of MYB TFs that play a key role in regulating genes related to photosynthesis and chloroplast biogenesis. Here, we summarized the current knowledge of the pleiotropic roles of GLKs in plants. In addition to their primary functions of controlling chloroplast biogenesis and function maintenance, GLKs have been proven to regulate the photomorphogenesis of seedlings, metabolite synthesis, flowering time, leaf senescence, and response to biotic and abiotic stress, ultimately contributing to crop yield. This review will provide a comprehensive understanding of the biological functions of GLKs and serve as a reference for future theoretical and applied studies of GLKs.