Abstract
Pentatricopeptide-repeat (PPR) proteins were identified as a type of nucleus coding protein that is composed of multiple tandem repeats. It has been reported that PPR genes play an important role in RNA editing, plant growth and development, and abiotic stresses in plants. However, the functions of PPR proteins remain largely unknown in soybean. In this study, 179 DYW subgroup PPR genes were identified in soybean genome (Glycine max Wm82.a2.v1). Chromosomal location analysis indicated that DYW subgroup PPR genes were mapped to all 20 chromosomes. Phylogenetic relationship analysis revealed that DYW subgroup PPR genes were categorized into three distinct Clusters (I to III). Gene structure analysis showed that most PPR genes were featured by a lack of intron. Gene duplication analysis demonstrated 30 PPR genes (15 pairs; ~35.7%) were segmentally duplicated among Cluster I PPR genes. Furthermore, we validated the mRNA expression of three genes that were highly up-regulated in soybean drought- and salt-induced transcriptome database and found that the expression levels of GmPPR4 were induced under salt and drought stresses. Under drought stress condition, GmPPR4-overexpressing (GmPPR4-OE) plants showed delayed leaf rolling; higher content of proline (Pro); and lower contents of H2O2, O2− and malondialdehyde (MDA) compared with the empty vector (EV)-control plants. GmPPR4-OE plants exhibited increased transcripts of several drought-inducible genes compared with EV-control plants. Our results provided a comprehensive analysis of the DYW subgroup PPR genes and an insight for improving the drought tolerance in soybean.
Highlights
The pentatricopeptide repeat (PPR) proteins containing tandem 30–40 amino acid sequence motifs, constitute a large gene family in plants [1]
We found that most PPR genes showed preferential accumulation in leaves compared to other tissues, which were likely to be responsible for their subcellular localization, and most reported PPR proteins were located in mitochondria or chloroplast
By examining the expression levels of DYW subgroup PPR genes according to soybean droughtand salt-induced transcriptome database, we found that three genes were highly up-regulated to drought and salt stresses
Summary
The pentatricopeptide repeat (PPR) proteins containing tandem 30–40 amino acid sequence motifs, constitute a large gene family in plants [1]. L motif and S motif contain 31 and 35 or 36 amino acid residues, respectively, which are considered to be variations of the P motif [2]. Most PPR proteins are highly conserved at the C-terminus and usually have three conserved domains at the C-terminus, E, E+ and DYW domains, respectively [3,4]. Based on these C-terminal domains, the PLS subfamily is divided into four subgroups, PLS subgroup, E subgroup, E+ subgroup, and DYW subgroup [2]. Members of the PPR family are widely distributed in plants and are large in number, they perform special functions [2]
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