Comparative expression analysis and characterization of the ethylene response factor in Cajanus cajan under the influence of Fusarium udum, NaCl and Pseudomonas fluorescens OKC

Abstract

We evaluated expression pattern of 34 pathogen stress-responsive pigeonpea CcERF genes (out of total 148 CcERF genes) under the combined stress of Fusarium udum WSP-V2 and NaCl in two pigeonpea cultivars, Asha (F. udum resistant) and Bahar (F. udum susceptible) in presence or absence of a plant growth-promoting rhizobacteria (PGPR) Pseudomonas fluorescens OKC. Expression analysis of the 34 CcERF genes in the pigeonpea cultivars revealed preferential transcript accumulation patterns of the CcERF genes in different treatments. Most of the CcERF genes responded well to individual stresses of WSP-V2 (32 CcERFs) and NaCl (30 CcERFs). Comparative assessment of the results from ‘Asha’ and ‘Bahar’ under pathogen stress indicates expression of three CcERF genes (CcERF5, CcERF9 and CcERF20) is important for resistance to F. udum WSP-V2. However, most of the genes that were up-regulated in the individual stresses of WSP-V2 and NaCl were down-regulated to the combined stresses, possibly due to cross-talk of the signaling pathways. Interestingly, application of P. fluorescens OKC up-regulated the expression of many CcERF genes which were down-regulated in the combined stress (WSP-V2 and NaCl). Considering the cumulative effects in both the OKC treated and non-treated plants in the two pigeonpea cultivars, CcERF14 is singled out as the most important dual responsive gene under the combined challenge of WSP-V2 and NaCl. Further, motif analysis of the CcERF genes resulted in identification of nine new motifs. Additionally, it was observed that motif (D/E) (V/I) (Q/R) XX(A/T) is conserved in CcERF5, QMI(E/D) Ell in CcERF9 and motifs RVWLGTFDTAEEAARAYDRAALAL and RGSKARLNFPE in CcERF9, CcERF20 and CcERF14.