In spite of increasing use in the food industry, high relative levels of palmitic acid (C16:0) in cottonseed oil imposes harmful effects on human health when overconsumed in the diet. The limited understanding of the mechanism in controlling fatty acid composition has become a significant obstacle for breeding novel cotton varieties with high-quality oil. Fatty acyl–acyl carrier protein (ACP) thioesterase B (FatBs) are a group of enzymes which prefer to hydrolyze the thioester bond from saturated acyl-ACPs, thus playing key roles in controlling the accumulation of saturated fatty acids. However, FatB members and their roles in cotton are largely unknown. In this study, a genome-wide characterization of FatB members was performed in allotetraploid upland cotton, aiming to explore the GhFatBs responsible for high accumulations of C16:0 in cotton seeds. A total of 14 GhFatB genes with uneven distribution on chromosomes were identified from an upland cotton genome and grouped into seven subfamilies through phylogenetic analysis. The six key amino acid residues (Ala, Trys, Ile, Met, Arg and Try) responsible for substrate preference were identified in the N-terminal acyl binding pocket of GhFatBs. RNA-seq and qRT-PCR analysis revealed that the expression profiles of GhFatB genes varied in multiple cotton tissues, with eight GhFatBs (GhA/D-FatB3, GhA/D-FatB4, GhA/D-FatB5, and GhA/D-FatB7) having high expression levels in developing seeds. In particular, expression patterns of GhA-FatB3 and GhD-FatB4 were positively correlated with the dynamic accumulation of C16:0 during cotton seed development. Furthermore, heterologous overexpression assay of either GhA-FatB3 or GhD-FatB4 demonstrated that these two GhFatBs had a high substrate preference to 16:0-ACP, thus contributing greatly to the enrichment of palmitic acid in the tested tissues. Taken together, these findings increase our understanding on fatty acid accumulation and regulation mechanisms in plant seeds. GhFatBs, especially GhA-FatB3 and GhD-FatB4, could be molecular targets for genetic modification to reduce palmitic acid content or to optimize fatty acid profiles in cotton and other oil crops required for the sustainable production of healthy edible oil.

Plant-specific GRAS transcription factors diversely participate in the regulation of multiple biological processes including growth and development, signal cross-talking and biotic/abiotic responses. However, this gene family was not characterized detailed in pepper ( Capsicum annuum L.), an economically important vegetable crop. Here, a total of 50 Ca GRAS members were identified in the pepper genome and renamed by their respective chromosomal distribution. Genomic organization revealed that most CaGRAS genes (84%) have no intron. A phylogenetic analysis was carried out using Arabidopsis thaliana to classify pepper GARS genes into at least ten subfamilies. Multiple sequence alignment showed GRAS-typical domains present in those proteins, with the members from the same phylogenetic subfamily exhibiting the similar motif composition. The presence of highly divergent N-terminus may be associated with functional specificity of each CaGRAS protein. Expression of 12 CaGRAS genes was not detected in all tissues tested, suggesting that their functions may be lost during evolution. By contrast, the rest 38 CaGRAS genes were expressed largely in several organs, showing their important roles in pepper life activities. Moreover, 21 CaGRAS genes were differentially expressed under cold, drought, salt and GA treatments, indicating that they play vital roles in response to abiotic stress in pepper. The first comprehensive analysis of GRAS gene family in the pepper genome in this study provide insights into understanding the CRAS-mediated regulation network, benefiting the genetic improvements in pepper and some other relative plants.PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3522v1 | CC BY 4.0 Open Access | rec: 11 Jan 2018, publ: 11 Jan 2018Genome-wide characterization and expression analysis of GRAS gene family in pepper (Capsicum annuum L.) Baolino Liu, Yan Sun, Jinai Xue, Runzhi Li* Institute of Molecular Aoriculture and Bioeneroy, Shanxi Aoricultural University, Shanxi 030801, P. R. China Abstract Plant-specific GRAS transcription factors diversely participate in the reoulation of multiple biolooical processes includino orowth and development, sional cross-talkino and biotic/abiotic responses. However, this oene family was not characterized detailed in pepper (Capsicum annuum L.), an economically important veoetable crop. Here, a total of 50 CaGRAS members were identified in the pepper oenome and renamed by their respective chromosomal distribution. Genomic oroanization revealed that most CaGRAS oenes (84%) have no intron. A phylooenetic analysis was carried out usino Arabidopsis thaliana to classify pepper GARS oenes into at least ten subfamilies. Multiple sequence alionment showed GRAS-typical domains present in those proteins, with the members from the same phylooenetic subfamily exhibitino the similar motif composition. The presence of hiohly diveroent N-terminus may be associated with functional specificity of each CaGRAS protein. Expression of 12 CaGRAS oenes was not detected in all tissues tested, s...

Plant-specific GRAS transcription factors diversely participate in the regulation of multiple biological processes including growth and development, signal cross-talking and biotic/abiotic responses. However, this gene family was not characterized detailed in pepper ( Capsicum annuum L.), an economically important vegetable crop. Here, a total of 50 Ca GRAS members were identified in the pepper genome and renamed by their respective chromosomal distribution. Genomic organization revealed that most CaGRAS genes (84%) have no intron. A phylogenetic analysis was carried out using Arabidopsis thaliana to classify pepper GARS genes into at least ten subfamilies. Multiple sequence alignment showed GRAS-typical domains present in those proteins, with the members from the same phylogenetic subfamily exhibiting the similar motif composition. The presence of highly divergent N-terminus may be associated with functional specificity of each CaGRAS protein. Expression of 12 CaGRAS genes was not detected in all tissues tested, suggesting that their functions may be lost during evolution. By contrast, the rest 38 CaGRAS genes were expressed largely in several organs, showing their important roles in pepper life activities. Moreover, 21 CaGRAS genes were differentially expressed under cold, drought, salt and GA treatments, indicating that they play vital roles in response to abiotic stress in pepper. The first comprehensive analysis of GRAS gene family in the pepper genome in this study provide insights into understanding the CRAS-mediated regulation network, benefiting the genetic improvements in pepper and some other relative plants.PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3522v1 | CC BY 4.0 Open Access | rec: 11 Jan 2018, publ: 11 Jan 2018Genome-wide characterization and expression analysis of GRAS gene family in pepper (Capsicum annuum L.) Baolino Liu, Yan Sun, Jinai Xue, Runzhi Li* Institute of Molecular Aoriculture and Bioeneroy, Shanxi Aoricultural University, Shanxi 030801, P. R. China Abstract Plant-specific GRAS transcription factors diversely participate in the reoulation of multiple biolooical processes includino orowth and development, sional cross-talkino and biotic/abiotic responses. However, this oene family was not characterized detailed in pepper (Capsicum annuum L.), an economically important veoetable crop. Here, a total of 50 CaGRAS members were identified in the pepper oenome and renamed by their respective chromosomal distribution. Genomic oroanization revealed that most CaGRAS oenes (84%) have no intron. A phylooenetic analysis was carried out usino Arabidopsis thaliana to classify pepper GARS oenes into at least ten subfamilies. Multiple sequence alionment showed GRAS-typical domains present in those proteins, with the members from the same phylooenetic subfamily exhibitino the similar motif composition. The presence of hiohly diveroent N-terminus may be associated with functional specificity of each CaGRAS protein. Expression of 12 CaGRAS oenes was not detected in all tissues tested, s...