Synchronised regulation of disease resistance in primed finger millet plants against the blast disease.

Plants, being sessile, are exposed to an array of abiotic and biotic stresses. To adapt towards the changing environments, plants have evolved mechanisms that help in perceiving stress signals wherein phytohormones play a critical role. They have the ability to network enabling them to mediate defense responses. These endogenous signals, functioning at low doses are a part of all the developmental stages of the plant. Phytohormones possess specific functions as they interact with each other positively or negatively through cross-talks. In the present study, variations in the amount of phytohormones produced during biotic stress caused due to Magnoporthe grisea infection was studied through targeted metabolomics in both primed and control finger millet plants. Histochemical studies revealed callose deposition at the site of pathogen entry in the primed plants indicating its role during plant defense. The knowledge on the genetic makeup during infection was obtained by quantification of MAP kinase kinases 1 and 2 (MKK1/2) and lipoxygenase (LOX) genes, wherein the expression levels were high in the primed plants at 6 hours post-inoculation (hpi) compared to mock-control. Studies indicate the pivotal role of mitogen-activated protein kinase (MAPK or MAP kinases) during defense signalling. It is the first report to be studied on MAPK role in finger millet-blast disease response. Temporal accumulation of LOX enzyme along with its activity was also investigated due to its significant role during jasmonate synthesis in the plant cells. Results indicated its highest activity at 12 hpi. This is the first report on the variation in phytohormone levels in fingermillet - M. grisea pathosystem upon priming which were substantiated through salicylic acid (SA) pathway.

In-silico analysis of cucumber (Cucumis sativus L.) Genome for WRKY transcription factors and cis-acting elements.

WRKY genes, comprises one among a large clan of transcription factor (TFs) genes in the plant kingdom, playing a fundamental role in the vegetative and reproductive growth, development and stress responses of a plant. In spite of several studies on cucumber (Cucumis sativus L.), WRKY genes and their interaction with stress response is limited. The present study, on the whole genome of cucumber was analyzed for WRKY genes which recognized 62 CsWRKY genes associated with the proteins obtained from lineages of supplementary plants. The physicochemical properties reveal the CsWRKY gene is ser-rich TF (6.70-18.40 %). The chromosomal distribution showed that all putative CsWRKY genes were distributed in seven chromosomes, enriched on chromosome 3 and 6 and least on chromosome 5. Based on phylogenetic analysis, along with motif determination and gene structure analysis, CsWRKYs are categorized as a Group I, II and III. The Group II further subdivided as Groups IIa-e. In the present study, it was observed that Group II WRKY-TFs was the largest group containing 43 WRKY genes containing a single WD (WRKY domain - WRKYGQK/WRKYGKK) and C2H2 type zinc finger structure (C-X4-5-C-X23-H-X1-H). The data also revealed that chromosome 3 and 5 contained all the three major groups and chromosome 6 contained I and II WRKY genes with uneven distribution. STRING analysis of selected CsWRKY proteins expressed in response to abiotic stress interacts with the CsMAPK proteins. Analysis of cis-acting elements and results suggest that CSWRKY genes play important role in response to biotic and abiotic stress. Response also predicted the candidate gene expression in cucumber during its development under different cellular condition.

Indole acetic acid production by fluorescent Pseudomonas spp. from the rhizosphere of Plectranthus amboinicus (Lour.) Spreng. and their variation in extragenic repetitive DNA sequences.

Fluorescent Pseudomonas (FP) is a heterogenous group of growth promoting rhizobacteria that regulate plant growth by releasing secondary metabolic compounds viz., indole acetic acid (IAA), siderophores, ammonia and hydrogen cyanide. In the present study, IAA producing FPs from the rhizosphere of Plectranthus amboinicus were characterized morphologically, biochemically and at the molecular level. Molecular identification of the isolates were carried out using Pseudomonas specific primers. The effect of varying time (24, 48, 72 and 96 h), Trp concentrations (100, 200, 300, 400 and 500 µg x ml(-1)), temperature (10, 26, 37 and 50 ± 2 degrees C) and pH (6, 7 and 8) on IAA production by 10 best isolates were studied. Results showed higher IAA production at 72 h incubation, at 300 µg x ml(-1) Trp concentration, temperature 26 ± 2 degrees C and pH 7. TLC with acidified ethyl acetate extract showed that the IAA produced has a similar Rf value to that of the standard IAA. Results of TLC were confirmed by HPLC analysis. Genetic diversity of the isolates was also studied using 40 RAPD and 4 Rep primers. Genetic diversity parameters such as dominance, Shannon index and Simpson index were calculated. Out of 40 RAPD primers tested, 9 (2 OP-D series and 7 OP-E series) were shortlisted for further analysis. Studies using RAPD, ERIC, BOX, REP and GTG5 primers revealed that isolates exhibit significant diversity in repetitive DNA sequences irrespective of the rhizosphere.