Studies on Plant Growth Promoting Properties of Fruit-Associated Bacteria from Elettaria cardamomum and Molecular Analysis of ACC Deaminase Gene.

Endophytic microorganisms have been reported to have diverse plant growth promoting mechanisms including phosphate solubilization, N2 fixation, production of phyto-hormones and ACC (1-aminocyclopropane-1-carboxylate) deaminase and antiphyto-pathogenic properties. Among these, ACC deaminase production is very important because of its regulatory effect on ethylene which is a stress hormone with precise role in the control of fruit development and ripening. However, distribution of these properties among various endophytic bacteria associated with fruit tissue and its genetic basis is least investigated. In the current study, 11 endophytic bacteria were isolated and identified from the fruit tissue of Elettaria cardamomum and were studied in detail for various plant growth promoting properties especially ACC deaminase activity using both culture-based and PCR-based methods. PCR-based screening identified the isolates EcB 2 (Pantoea sp.), EcB 7 (Polaromonas sp.), EcB 9 (Pseudomonas sp.), EcB 10 (Pseudomonas sp.) and EcB 11 (Ralstonia sp.) as positive for ACC deaminase. The PCR products were further subjected to sequence analysis which proved the similarity of the sequences identified in the study with ACC deaminase sequences reported from other sources. The detailed bioinformatic analysis of the sequence including homology-based modelling and molecular docking confirmed the sequences to have ACC deaminase activity. The docking of the modelled proteins was done using patch dock, and the detailed scrutiny of the protein ligand interaction revealed conservation of key amino acids like Lys51, Ser78, Tyr268 and Tyr294 which play important role in the enzyme activity. These suggest the possible regulatory effect of these isolates on fruit physiology.

Occurrence of trypsin-like protease in cardamom (Elettaria cardamomum Maton).

Occurrence of trypsin-like protease in fresh cardamom (Elettaria cardamomum Maton) seeds, as evidenced by the benzoyl-arg-p-nitroanilide (BApNA) hydrolyzing ability of the seed enzyme preparation under alkaline condition is reported for the first time. The enzyme has a pH and temperature optima as 8 and 45 degrees C, respectively. It is inhibited by aprotinin and phenylmethyl sulfonyl fluoride (PMSF) in a dose-dependent manner, suggesting the presence of serine residues at the active site. The enzyme had a V(max) of 98.01 nmoles p-nitroaniline released per min per mg protein and K(m) of 0.0684 mM with BApNA as substrate. Addition of aprotinin (75.75 microM) increased K(m) value by three-folds, whereas the V(max) was reduced by 23%.