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Research Project: Genetic Mechanisms and Improvement of Insect Resistance in Wheat, Barley, and Sorghum

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Title: Identification and characterization of plant resistance genes (R genes) in sorghum and their involvement in plant defense against aphids

item ZHANG, HENGYOU - Oklahoma State University
item HUANG, JIAN - Oklahoma State University
item Huang, Yinghua

Submitted to: Plant Growth Regulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2022
Publication Date: 1/22/2022
Citation: Zhang, H., Huang, J., Huang, Y. 2022. Identification and characterization of plant resistance genes (R genes) in sorghum and their involvement in plant defense against aphids. Plant Growth Regulation. 96:443-461.

Interpretive Summary: Plant diseases and pests can cause destructive damages to plants and reduce crop yields when the outbreaks are getting severe. Resistance (R) genes exist naturally in some plants, which can detect attack from pathogens or pests and then provide a counter action against those enemies. Little is known about the resistance genes in sorghum though numerous plant R-genes have been reported in other plant species. Identifying new sources of resistance to pests has been one of the main research objectives of ARS scientists in Stillwater, Oklahoma. In this paper, they report the identification of 548 resistance genes in the genome of sorghum (Sorghum bicolor (L.) Moench) through the genome-wide sequence analysis. They further examined the gene structures at the sequence level and elucidated the relationship between members of this gene family. As for their function, it is believed that those R-genes possess a wide range of biological functions in plant growth and defense, and some of them may hold a specific ability to tackle certain target(s). Based on the results of expression analysis, 19 of those genes showed differential expression in response to infestation by greenbug biotype I (Gb-I). Particularly, two R-genes were validated by quantitative real time PCR (qRT-PCR) for their upregulation against aphids. Overall, the results presented here represent a valuable resource for both designing experiments to further confirm the function of the candidate genes regulating plant-aphid interactions and developing sorghum crop with improved insect resistance.

Technical Abstract: Plants are constantly exposed to numerous biotic stresses; thus, they have evolved to defend themselves from their enemies such as pathogen or insect pests. Plant resistance (R) genes encoded by nucleotide binding site-leucine rich repeat (NBSLRR)or LRR-containing transmembrane-receptor proteins play important roles in plant defense against various biotic stresses. In this paper, we report the identification of 308 R genes, including NBS-LRR, 175 genes encoding receptor-like kinases (RLKs) and 65 genes coding for receptor-like proteins (RLPs) in sorghum [Sorghum bicolor (L.) Moench] through genome-wide sequence analysis. Those genes were dispersed across all ten chromosomes of sorghum. Phylogenetic analysis of the newly identified NBS-LRR, RLP and RLK genes classified them into five, eleven, and six clades, respectively, of which region-specific subclades were established. Investigation of exon/intron organization demonstrates the variations in number and location of introns within the family, and the genes that evolved close to their originals share identical gene structures. Also, gene duplication was noted, including 142 pairs of duplicated genes in the NBS family, 12 RLK genes and one RLP gene, respectively. Chromosomal locations analysis of these newly-identified R genes and 17 published QTLs indicated two hot-spot regions referring resistance to at least two biotic stresses. Among those R genes, some of them showed significantly differential expression during the infestation by greenbug biotype I based on the expression profile. Particularly, three R genes were validated by quantitative real time PCR for their up-regulation in response to aphids. In summary, the results of this study contribute not only a valuable genetic resource for further functional characterization of those newly-identified R genes, but also provide insight into genetic improvement of sorghum for resistance to greenbug aphids.