Salicylic Acid-Induced Expression Profiles of LRR and LRR-RLK Candidate Genes Modulate Mungbean Yellow Mosaic India Virus Resistance in Blackgram and Its Two Wild Non-Progenitors

Abstract

Blackgram is an important short-duration grain legume, but its yield is highly affected by various stresses. Among biotic stresses, yellow mosaic disease (YMD) is known as a devastating disease that leads to 100% yield loss under severe conditions. The cultivated lines possess resistance, but exploring more diverse sources of resistance may be useful for pyramiding to improve the durability of said resistance. Some wild Vigna species have potentially demonstrated a high level of resistance. R-genes, including gene families of leucine-rich repeats (LRRs) and leucine-rich repeat receptor-like kinases (LRR-RLKs), are known for modulating the resistance in plants against various biotic stresses. The first comprehensive analysis of the LRR and LRR-RLK gene families in mungbean is reported in the present study. A total of forty-six candidate genes were identified and grouped into eight clades. Protein motif analysis showed that the "Pkinase domain" and "LRR domains" were conserved in most of the R-proteins. The expression of candidate genes viz. VrNBS_TNLRR-8, VrLRR_RLK-20, VrLRR_RLK-17, and VrLRR_RLK-19 demonstrated significantly up-regulated expression upon YMD infection in control and salicylic acid-primed (SA-primed) plants. The analysis provides insight into the diversity and robust candidate genes for functional studies modulating YMD resistance altered by salicylic acid.

Keywords: LRR-RLK; R-genes; YMD; gene expression; qRT-PCR; salicylic acid.

Figure 1

Physical mapping of LRR and LRR-RLK genes on different chromosomes.

Figure 2

Phylogenetic tree of different LRR and LRR-RLK genes by adopting maximum livelihood model with bootstrap value n = 1000 using MEGA 11.0.

Figure 3

(a) Gene structure of different LRR and LRR-RLK genes. The blue line indicates the upstream/downstream regions; the red color indicates the CDS region; black lines denote introns. (b) Conserved domain architecture of different LRR and LRR-RLK genes.

Figure 3

(a) Gene structure of different LRR and LRR-RLK genes. The blue line indicates the upstream/downstream regions; the red color indicates the CDS region; black lines denote introns. (b) Conserved domain architecture of different LRR and LRR-RLK genes.

Figure 4

Motif analysis of VrNBS-LRR encoding genes.

Figure 4

Motif analysis of VrNBS-LRR encoding genes.

Figure 5

In silico gene expression profile of LRR and LRR-RLK candidates in different tissues of Vigna unguiculata using expression atlas. S8, S10, S14, and S18 are developing seeds.

Figure 6

(a) qRT-PCR analysis of LRR candidate genes (A) VrNBS_CNLRR-1; (B) VrNBS_CNLRR-4; (C) VrNBS_NLRRcc-5; (D) VrNBS_TNLRR-8; (E) VrNBS_NLRRtir-11 under control and MYMIV infection in untreated and SA-treated genotypes. (b) qRT-PCR analysis of LRR-RLK candidate genes (F) VrLRR_RLK-16; (G) VrLRR_RLK-17; (H) VrLRR_RLK-18; (I) VrLRR_RLK-19 under control and MYMIV infection in untreated and SA-treated genotypes. (c) qRT-PCR analysis of LRR-RLK candidate genes (J) VrLRR_RLK-20; (K) VrLRR_RLK-21; (L) VrLRR_RLK-31 under control and MYMIV infection in untreated and SA-treated genotypes. The different letters in the graph showed significant differences among them.

Figure 6

(a) qRT-PCR analysis of LRR candidate genes (A) VrNBS_CNLRR-1; (B) VrNBS_CNLRR-4; (C) VrNBS_NLRRcc-5; (D) VrNBS_TNLRR-8; (E) VrNBS_NLRRtir-11 under control and MYMIV infection in untreated and SA-treated genotypes. (b) qRT-PCR analysis of LRR-RLK candidate genes (F) VrLRR_RLK-16; (G) VrLRR_RLK-17; (H) VrLRR_RLK-18; (I) VrLRR_RLK-19 under control and MYMIV infection in untreated and SA-treated genotypes. (c) qRT-PCR analysis of LRR-RLK candidate genes (J) VrLRR_RLK-20; (K) VrLRR_RLK-21; (L) VrLRR_RLK-31 under control and MYMIV infection in untreated and SA-treated genotypes. The different letters in the graph showed significant differences among them.

Figure 6

(a) qRT-PCR analysis of LRR candidate genes (A) VrNBS_CNLRR-1; (B) VrNBS_CNLRR-4; (C) VrNBS_NLRRcc-5; (D) VrNBS_TNLRR-8; (E) VrNBS_NLRRtir-11 under control and MYMIV infection in untreated and SA-treated genotypes. (b) qRT-PCR analysis of LRR-RLK candidate genes (F) VrLRR_RLK-16; (G) VrLRR_RLK-17; (H) VrLRR_RLK-18; (I) VrLRR_RLK-19 under control and MYMIV infection in untreated and SA-treated genotypes. (c) qRT-PCR analysis of LRR-RLK candidate genes (J) VrLRR_RLK-20; (K) VrLRR_RLK-21; (L) VrLRR_RLK-31 under control and MYMIV infection in untreated and SA-treated genotypes. The different letters in the graph showed significant differences among them.

Figure 7

Protein structure prediction of selected LRR and LRR-RLK candidate genes.

Figure 8

Protein–protein interaction network based on STRING database of the selected genes.