Induction of Drought Stress Resistance by Multi-Functional PGPR Bacillus licheniformis K11 in Pepper

Abstract

Drought stress is one of the major yield affecting factor for pepper plant. The effects of PGPRs were analyzed in relation with drought resistance. The PGPRs inoculated pepper plants tolerate the drought stress and survived as compared to non-inoculated pepper plants that died after 15 days of drought stress. Variations in protein and RNA accumulation patterns of inoculated and non-inoculated pepper plants subjected to drought conditions for 10 days were confirmed by two dimensional polyacrylamide gel electrophoresis (2D-PAGE) and differential display PCR (DD-PCR), respectively. A total of six differentially expressed stress proteins were identified in the treated pepper plants by 2D-PAGE. Among the stress proteins, specific genes of Cadhn, VA, sHSP and CaPR-10 showed more than a 1.5-fold expressed in amount in B. licheniformis K11-treated drought pepper compared to untreated drought pepper. The changes in proteins and gene expression patterns were attributed to the B. licheniformis K11. Accordingly, auxin and ACC deaminase producing PGPR B. licheniformis K11 could reduce drought stress in drought affected regions without the need for overusing agrochemicals and chemical fertilizer. These results will contribute to the development of a microbial agent for organic farming by PGPR.

Keywords: PGPR; drought stress tolerance; pepper.

Fig. 1

Induction of drought stress resistance of red-pepper in response to treatment with B. licheniformis K11. (A) plant picture, (B) root length, (C) shoot length, (D) dry weight. B. licheniformis K11 was once treated with 7.0 × 10⁸ cfu/ml per pot. The positive control was watered every 3 days with 50 ml of sterile water. The pictures were taken at the age of 10 days. Values are expressed as the means of three replicates, each containing 10 plants. Statistical analysis was performed by ANOVA and Duncan’s multiple range test. Standard errors were determined at P ≤ 0.05.

Fig. 2

Proteome analysis of the drought stress-related proteins in pepper roots. Drought, drought stress alone for 10 days; Water, watering condition; K11, drought stress with B. licheniformis K11 inoculation (10⁸ cell/pot). In the first dimention, 100 μg of protein was loaded on an 18 cm IPG strip with a linear gradient of pH 4.0 – 10.0 and SDS-PAGE gels were used in the second dimension. The red spots represent the proteins that showed significant differential expression under drought stress with B. licheniformis K11 inoculation as compared with water treatment (A). (B) The differential abundance of proteins was quantified using PDQuest software and plotted as the relative intensity. The white, tilt lines, and square bars indicate water treatments, drought stress without inoculation, and drought stress with inoculation, respectively. Values are the mean ± SE from three replicates. Statistical analysis was performed by ANOVA and Duncan’s multiple range test. Standard errors were determined at P ≤ 0.05.

Fig. 3

Comparative analysis of stress-related genes in pepper roots under drought stress. Drought, drought stress alone, for 10 days; Water, watering condition; K11, drought stress with B. licheniformis K11 inoculation (10⁸ cell/pot). mRNA differential display analysis of total RNA isolated from pepper roots treated with drought stress. Total RNAs were reverse-transcribed with the primer of stress tolerance-related genes.