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Identification and molecular characterization of the nicotianamine synthase gene family in bread wheat.

ABSTRACT: Nicotianamine (NA) is a non-protein amino acid involved in fundamental aspects of metal uptake, transport and homeostasis in all plants and constitutes the biosynthetic precursor of mugineic acid family phytosiderophores (MAs) in graminaceous plant species. Nicotianamine synthase (NAS) genes, which encode enzymes that synthesize NA from S-adenosyl-L-methionine (SAM), are differentially regulated by iron (Fe) status in most plant species and plant genomes have been found to contain anywhere from 1 to 9 NAS genes. This study describes the identification of 21 NAS genes in the hexaploid bread wheat (Triticum aestivum L.) genome and their phylogenetic classification into two distinct clades. The TaNAS genes are highly expressed during germination, seedling growth and reproductive development. Fourteen of the clade I NAS genes were up-regulated in root tissues under conditions of Fe deficiency. Protein sequence analyses revealed the presence of endocytosis motifs in all of the wheat NAS proteins as well as chloroplast, mitochondrial and secretory transit peptide signals in four proteins. These results greatly expand our knowledge of NAS gene families in graminaceous plant species as well as the genetics underlying Fe nutrition in bread wheat.

SUBMITTER: Bonneau J

PROVIDER: S-EPMC5103229 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Identification and molecular characterization of the nicotianamine synthase gene family in bread wheat.

Bonneau Julien J Baumann Ute U Beasley Jesse J Li Yuan Y Johnson Alexander A T AA

Plant biotechnology journal 20160620 12

Nicotianamine (NA) is a non-protein amino acid involved in fundamental aspects of metal uptake, transport and homeostasis in all plants and constitutes the biosynthetic precursor of mugineic acid family phytosiderophores (MAs) in graminaceous plant species. Nicotianamine synthase (NAS) genes, which encode enzymes that synthesize NA from S-adenosyl-L-methionine (SAM), are differentially regulated by iron (Fe) status in most plant species and plant genomes have been found to contain anywhere from ...[more]

PMID: 27155533

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Project description:BACKGROUND: Nicotianamine (NA), a ubiquitous molecule in plants, is an important metal ion chelator and the main precursor for phytosiderophores biosynthesis. Considerable progress has been achieved in cloning and characterizing the functions of nicotianamine synthase (NAS) in plants including barley, Arabidopsis and rice. Maize is not only an important cereal crop, but also a model plant for genetics and evolutionary study. The genome sequencing of maize was completed, and many gene families were identified. Although three NAS genes have been characterized in maize, there is still no systematic identification of maize NAS family by genomic mining. RESULTS: In this study, nine NAS genes in maize were identified and their expression patterns in different organs including developing seeds were determined. According to the evolutionary relationship and tissue specific expression profiles of ZmNAS genes, they can be subgrouped into two classes. Moreover, the expression patterns of ZmNAS genes in response to fluctuating metal status were analysed. The class I ZmNAS genes were induced under Fe deficiency and were suppressed under Fe excessive conditions, while the expression pattern of class II genes were opposite to class I. The complementary expression patterns of class I and class II ZmNAS genes confirmed the classification of this family. Furthermore, the histochemical localization of ZmNAS1;1/1;2 and ZmNAS3 were determined using in situ hybridization. It was revealed that ZmNAS1;1/1;2, representing the class I genes, mainly expressed in cortex and stele of roots with sufficient Fe, and its expression can expanded in epidermis, as well as shoot apices under Fe deficient conditions. On the contrary, ZmNAS3, one of the class II genes, was accumulated in axillary meristems, leaf primordia and mesophyll cells. These results suggest that the two classes of ZmNAS genes may be regulated on transcriptional level when responds to various demands for iron uptake, translocation and homeostasis. CONCLUSION: These results provide significant insights into the molecular bases of ZmNAS in balancing iron uptake, translocation and homeostasis in response to fluctuating environmental Fe status.

Project description:BACKGROUND:Ascorbate is a powerful antioxidant in plants and an essential micronutrient for humans. The GDP-L-galactose phosphorylase (GGP) gene encodes the rate-limiting enzyme of the L-galactose pathway-the dominant ascorbate biosynthetic pathway in plants-and is a promising gene candidate for increasing ascorbate in crops. In addition to transcriptional regulation, GGP production is regulated at the translational level through an upstream open reading frame (uORF) in the long 5'-untranslated region (5'UTR). The GGP genes have yet to be identified in bread wheat (Triticum aestivum L.), one of the most important food grain sources for humans. RESULTS:Bread wheat chromosomal groups 4 and 5 were found to each contain three homoeologous TaGGP genes on the A, B, and D subgenomes (TaGGP2-A/B/D and TaGGP1-A/B/D, respectively) and a highly conserved uORF was present in the long 5'UTR of all six genes. Phylogenetic analyses demonstrated that the TaGGP genes separate into two distinct groups and identified a duplication event of the GGP gene in the ancestor of the Brachypodium/Triticeae lineage. A microsynteny analysis revealed that the TaGGP1 and TaGGP2 subchromosomal regions have no shared synteny suggesting that TaGGP2 may have been duplicated via a transposable element. The two groups of TaGGP genes have distinct expression patterns with the TaGGP1 homoeologs broadly expressed across different tissues and developmental stages and the TaGGP2 homoeologs highly expressed in anthers. Transient transformation of the TaGGP coding sequences in Nicotiana benthamiana leaf tissue increased ascorbate concentrations more than five-fold, confirming their functional role in ascorbate biosynthesis in planta. CONCLUSIONS:We have identified six TaGGP genes in the bread wheat genome, each with a highly conserved uORF. Phylogenetic and microsynteny analyses highlight that a transposable element may have been responsible for the duplication and specialized expression of GGP2 in anthers in the Brachypodium/Triticeae lineage. Transient transformation of the TaGGP coding sequences in N. benthamiana demonstrated their activity in planta. The six TaGGP genes and uORFs identified in this study provide a valuable genetic resource for increasing ascorbate concentrations in bread wheat.

Project description:BACKGROUND:Flavonoid compounds are secondary plant metabolites, having a functional importance in plant development, protection from pathogens and unfavorable environmental factors. Chalcone synthase (CHS) is a key enzyme in the biosynthesis of flavonoids; it is involved in biosynthesis of all classes of flavonoid compounds. Nevertheless, the Chs gene family in bread wheat (Triticum aestivum L.) has been not characterized yet. The aim of the current study was to investigate structural and functional organization of the Chs genes and evolution of this gene family in bread wheat and relative species. RESULTS:The nucleotide sequences of the eight Chs copies in T. aestivum were identified. Among them, two homoeologous sets of the Chs genes were located on the short (Chs-A1, -B1, -D1) and the long (Chs-A4, -B4, -D4) arms of homoeologous group 2 chromosomes. Two paralogous gene copies in the B-genome (Chs-B2, -B3) were located in the distal regions of 2BS chromosome. To clarify the origin of Chs duplications in the B-genome the phylogenetic analysis with the Chs sequences of Triticum and Aegilops species carrying ancestral genomes was conducted. It was estimated that the first duplication event occurred in the genome of the common ancestor of Triticum and Aegilops genera about 10-12 million years ago (MYA), then another copy was formed in the ancestor of the B-genome about 6-7 MYA. A homology modeling revealed high sequence similarity of bread wheat CHS enzymes. A number of short deletions in coding regions of some Chs sequences are not expected to have any significant functional effects. Estimation of transcriptional activity of the Chs copies along with a comparative analysis of their promoters structure suggested their functional specialization, which likely contributed to the maintaining of the duplicated Chs genes in wheat genome. CONCLUSIONS:From possible ten Chs copies in bread wheat genome, eight members of this family retained their intact structure and activity, while two copies appear to be lost at the level of diploid and tetraploid ancestors. Transcriptional assay along with a comparative analysis of the cis-regulatory elements revealed their functional diversification. The multiple functions supported by the Chs family are assumed to be a driving force for duplications of the Chs gene and their retention in plant genome.

Dataset Information

Identification and molecular characterization of the nicotianamine synthase gene family in bread wheat.

Publications

Identification and molecular characterization of the nicotianamine synthase gene family in bread wheat.

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