Comparative transcriptome profiling of two maize near-isogenic lines differing in the allelic state for bacterial brown spot disease resistance

The bacterial brown spot disease（BBS）, caused primarily by Pseudomonas syringae pv. syringae van Hall（Pss）, reduces plant vigor, yield and quality in maize. To reveal the nature of the defense mechanisms and identify genes involved in the effective host resistance, the dynamic changes of defense transcriptome triggered by the infection of Pss were investigated and compared between two maize near-isogenic lines（NILs）. We found that Pss infection resulted in a sophisticated transcriptional reprogramming of several biological processes and the resistant NIL employed much faster defense responses than the susceptible NIL. Numerous genes encoding essential components of plant basal resistance would be able to be activated in the susceptible NIL, such as PEN1, PEN2, PEN3, and EDR1, however, in a basic manner, such resistance might not be sufficient for suppressing Pss pathogenesis. In addition, the expressions of a large number of PTI-, ETI-, PR-, and WRKY-related genes were pronouncedly activated in the resistant NIL, suggesting that maize employ a multitude of defense pathways to defend Pss infection. Six R-gene homologs were identified to have significantly higher expression levels in the resistant NIL at early time point, indicating that a robust surveillance system（gene-to-gene model） might operate in maize during Pss attacks, and these homolog genes are likely to be potential candidate resistance genes involved in BBS disease resistance. Furthermore, a holistic group of novel pathogen-responsive genes were defined, providing the repertoire of candidate genes for further functional characterization and identification of their regulation patterns during pathogen infection.

Characterization of the Rice Canopy Infested with Brown Spot Disease Using Field Hyperspectral Data

Based on the field hyperspectral data from the analytical spectral devices （ASD） spectrometer, we characterized the spectral properties of rice canopies infested with brown spot disease and selected spectral regions and bands sensitive to four severity degrees （severe, moderate, light, and healthy）. The results show that the curves＇ variation on the original and the first- and second-order de- rivative curves are greatly different, but the spectral difference in the near-infrared region is the most obvious for each level. Specifically, the peaks are located at 822, 738, and 793 nm, while the valleys are located at 402, 570, and 753 run, respectively. The sensitive regions are between 430-520, 530-550, and 650-710 nm, and the bands are 498, 539, and 673 nm in the sensitivity analysis, while they are in the ranges of 401-530, 550-730 as well as at 498 nm and 678 nm in the continuum removal.

Involvement of NAC transcription factor NaNAC29 in Alternaria alternata resistance and leaf senescence in Nicotiana attenuata

NAC-LIKE,ACTIVATED BY AP3/PI(NAP)is a NAC transcription factor regulating leaf senescence in Arabidopsis thaliana.In wild tobacco Nicotiana attenuata,a nuclear localized NAC transcription factor NaNAC29 was identified to be highly elicited after inoculation of Alternaria alternata,a notorious necrotic fungus on tobacco species.The NaNAC29 possesses similar tertiary structure to NAP with 60%amino acid identity.However,it remains unknown the role of NaNAC29 in plant defense responses to A.alternata and leaf senescence in N.attenuata.In this paper,Defensin-like protein 1(NaDLP1)was highly induced in N.attenuata after A.alternata inoculation and bigger lesions were developed in NaDLP1-silenced plants.Interestingly,A.alternata-induced NaDLP1 was reduced by 76%in VIGS NaNAC29 plants and by 61%in JA deficient irAOC plants at 3 days post inoculation.The regulation of NaDLP1 expression by NaNAC29 was clearly independent on JA pathway,since exogenous methyl jasmonate treatment could not complement the induction levels of NaDLP1 in NaNAC29-silenced plants to the levels in WT plants.Otherwise,the expression of NaNAC29 was low expressed in young leaves but highly in senescent leaves and darktreated leaves.NaNAC29-silenced plants,which were generated by virus-induced gene silencing(VIGS NaNAC29),showed delayed senescence phenotype.In addition,constitutive over-expression of NaNAC29 in A.thaliana could rescue the delayed-senescence phenotype of nap and caused precocious leaf senescence of wild-type Col-0 plants.All the data above demonstrate that NaNAC29 is a NAP homolog in N.attenuata participating in the defense responses to A.alternata by regulation of a defensin protein NaDLP1 and promoting leaf senescence.