Molecular progress on the mapping and cloning of functional genes for blast disease in rice (Oryza sativa L.): current status and future considerations

Genome-wide identification and characterization of the HD-Zip gene family and expression analysis in response to stress in Rehmannia glutinosa Libosch

The HD-Zip family of transcription factors is unique to the plant kingdom, and play roles in modulation of plant growth and response to environmental stresses. R. glutinosa is an important Chinese medicinal material. Its yield and quality are susceptible to various stresses. The HD-Zip transcription factors is unique to the plant, and roles in modulation of plant growth and response to environmental stresses. However, there is no relevant research on the HD-ZIP of R. glutinosa. In this study, 92 HD-Zip transcription factors were identified in R. glutinosa, and denominated as RgHDZ1-RgHDZ92. Members of RgHDZ were classified into four groups (HD-ZipI-IV) based on the phylogenetic relationship of Arabidopsis HD-Zip proteins, and each group contains 38, 18, 17, and 19 members, respectively. Expression analyses of RgHDZ genes based on transcriptome data showed that the expression of these genes could be induced by the endophytic fungus of R. glutinosa. Additionally, we showed that RgHDZ genes were differentially expressed in response to drought, waterlogging, temperature, and salinity treatments. This study provides important information for different expression patterns of stress-responsive HD-Zip and may contribute to the better understanding of the different responses of plants to biotic and abiotic stresses, and provide a molecular basis for the cultivation of resistant varieties of R. glutinosa.

Fine mapping of a panicle blast resistance gene Pb-bd1 in Japonica landrace Bodao and its application in rice breeding

BACKGROUND

Rice blast caused by Magnaporthe oryzae is the most devastating disease in rice production. Compared with seedling blast, panicle blast is considered to be more destructive, which can occur without being preceded by severe seedling blast. However, panicle blast resistance research is rarely reported.

RESULTS

Bodao, a japonica landrace from Taihu Lake region, showed a high level of panicle blast resistance. In this study, a mapping population of 212 recombination inbreeding lines (RILs) was developed from a cross of Bodao and the susceptible cultivar Suyunuo, and the RILs were evaluated for panicle blast resistance in three trials. Two quantitative trait loci (QTLs) qPb11-1 and qPb6-1 for panicle-blast resistance were identified, including a major QTL qPb11-1 (Pb-bd1) on chromosome 11 of Bodao explaining from 55.31% to 71.68% of the phenotype variance, and a minor QTL qPb6-1 on chromosome 6 of Suyunuo explaining from 3.54% to 6.98% of the phenotype variance. With the various segregation populations, Pb-bd1 was fine mapped in a 40.6 Kb region flanked by markers BS83 and BS98, and six candidate genes were identified within this region, including one gene encoding NAC domain-containing protein, one gene encoding unknown expression proteins, two genes encoding nucleotide binding site-leucine rich repeat (NBS-LRR) type disease resistance proteins, and two genes encoding von Willebrand factor type A (VWA) domain containing proteins. For application in rice breeding, three introgression lines of Pb-bd1with significantly enhanced panicle blast resistance were developed by using molecular assisted method (MAS) from the commercial variety Nanjing46 (NJ46).

CONCLUSION

Two QTLs, qPb11-1(Pb-bd1) and qPb6-1 conferring panicle blast resistance, were identified from japonica landrace Bodao and Suyunuo.qPb11-1(Pb-bd1) was fine mapped in a 40.6 Kb region flanked by marker BS83 and BS98. Three introgression lines of Pb-bd1with significantly enhanced panicle blast resistance were developed by MAS method from the commercial variety NJ46. It indicated that Pb-bd1 would be useful gene source in panicle blast resistance breeding.

Autoimmunity in plants

Attenuation in the activity of the negative regulators or the hyperactivity of plant innate immune receptors often causes ectopic defense activation manifested in severe growth retardation and spontaneous lesion formations, referred to as autoimmunity. In this review, we have described the cellular and molecular basis of the development of autoimmune responses for their useful applications in plant defense. Plants are exposed to diverse disease-causing pathogens, which bring infections by taking over the control on host immune machineries. To counter the challenges of evolving pathogenic races, plants recruit specific types of intracellular immune receptors that mostly belong to the family of polymorphic nucleotide-binding oligomerization domain-containing leucine-rich repeat (NLR) proteins. Upon recognition of effector molecules, NLR triggers hyperimmune signaling, which culminates in the form of a typical programmed cell death, designated hypersensitive response. Besides, few plant NLRs also guard certain host proteins known as 'guardee' that are modified by effector proteins. However, this fine-tuned innate immune system can be lopsided upon knock-out of the alleles that correspond to the host guardees, which mimick the presence of pathogen. The absence of pathogens causes inappropriate activation of the respective NLRs and results in the constitutive activation of plant defense and exhibiting autoimmunity. In plants, autoimmune mutants are readily scorable due to their dwarf phenotype and development of characteristic macroscopic disease lesions. Here, we summarize recent reports on autoimmune response in plants, how it is triggered, and phenotypic consequences associated with this phenomenon.