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Diversification of genes encoding granule-bound starch synthase in monocots and dicots is marked by multiple genome-wide duplication events.

ABSTRACT: Starch is one of the major components of cereals, tubers, and fruits. Genes encoding granule-bound starch synthase (GBSS), which is responsible for amylose synthesis, have been extensively studied in cereals but little is known about them in fruits. Due to their low copy gene number, GBSS genes have been used to study plant phylogenetic and evolutionary relationships. In this study, GBSS genes have been isolated and characterized in three fruit trees, including apple, peach, and orange. Moreover, a comprehensive evolutionary study of GBSS genes has also been conducted between both monocots and eudicots. Results have revealed that genomic structures of GBSS genes in plants are conserved, suggesting they all have evolved from a common ancestor. In addition, the GBSS gene in an ancestral angiosperm must have undergone genome duplication ?251 million years ago (MYA) to generate two families, GBSSI and GBSSII. Both GBSSI and GBSSII are found in monocots; however, GBSSI is absent in eudicots. The ancestral GBSSII must have undergone further divergence when monocots and eudicots split ?165 MYA. This is consistent with expression profiles of GBSS genes, wherein these profiles are more similar to those of GBSSII in eudicots than to those of GBSSI genes in monocots. In dicots, GBSSII must have undergone further divergence when rosids and asterids split from each other ?126 MYA. Taken together, these findings suggest that it is GBSSII rather than GBSSI of monocots that have orthologous relationships with GBSS genes of eudicots. Moreover, diversification of GBSS genes is mainly associated with genome-wide duplication events throughout the evolutionary course of history of monocots and eudicots.

SUBMITTER: Cheng J

PROVIDER: S-EPMC3264551 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Diversification of genes encoding granule-bound starch synthase in monocots and dicots is marked by multiple genome-wide duplication events.

Cheng Jun J Khan Muhammad Awais MA Qiu Wen-Ming WM Li Jing J Zhou Hui H Zhang Qiong Q Guo Wenwu W Zhu Tingting T Peng Junhua J Sun Fengjie F Li Shaohua S Korban Schuyler S SS Han Yuepeng Y

PloS one 20120123 1

Starch is one of the major components of cereals, tubers, and fruits. Genes encoding granule-bound starch synthase (GBSS), which is responsible for amylose synthesis, have been extensively studied in cereals but little is known about them in fruits. Due to their low copy gene number, GBSS genes have been used to study plant phylogenetic and evolutionary relationships. In this study, GBSS genes have been isolated and characterized in three fruit trees, including apple, peach, and orange. Moreover ...[more]

PMID: 22291904

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Project description:Starch Synthase (SS) plays an important role in extending the ?-1,4 glucan chains during starch biosynthesis by catalyzing the transfer of the glucosyl moiety from ADP-glucose to the non-reducing end of a pre-existing glucan chain. SS has five distinct isoforms of which SSIII is involved in the formation of longer glucan chain length. Here we report identification and detailed characterization of 'true' orthologs of the well-characterized maize SSIII (ZmSSIII), among six monocots and two dicot species. ZmSSIII orthologs have nucleotide sequence similarity ranging from 56-81%. Variation in gene size among various orthologs ranged from 5.49 kb in Arabidopsis to 11.62 kb in Brachypodium and the variation was mainly due to intron size and indels present in the exons 1 and 3. Number of exons and introns were highly conserved among all orthologs however. While the intron number was conserved, intron phase showed variation at group, genera and species level except for intron 1 and 5. Several species, genera, and class specific cis-acting regulatory elements were identified in the promoter region. The predicted protein size of the SSIII orthologs ranged from 1094 amino acid (aa) in Arabidopsis to 1688 aa in Brachypodium with sequence identity ranging from 60%-89%. The N-terminal region of the protein was highly variable whereas the C-terminal region containing the Glycosyltransferase domain was conserved with >80% sequence similarity among the orthologs. In addition to confirming the known motifs, eleven novel motifs possibly providing species, genera and group specific functions, were identified in the three carbohydrate binding domains. Despite of significant sequence variation among orthologs, most of the motifs and their relative distances are highly conserved among the orthologs. The 3-D structure of catalytic region of SSIII orthologs superimposed with higher confidence confirming the presence of similar binding sites with five unidentified conserved regions in the catalytic (glycosyltransferase) domain including the pockets involved in catalysis and binding of ligands. Homeologs of wheat SSIII gene showed tissue and developmental stage specific expression pattern with the highest expression recorded in developing grains.

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Dataset Information

Diversification of genes encoding granule-bound starch synthase in monocots and dicots is marked by multiple genome-wide duplication events.

Publications

Diversification of genes encoding granule-bound starch synthase in monocots and dicots is marked by multiple genome-wide duplication events.

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