Dataset Information

Repetitive DNA in the pea (Pisum sativum L.) genome: comprehensive characterization using 454 sequencing and comparison to soybean and Medicago truncatula.

ABSTRACT: BACKGROUND: Extraordinary size variation of higher plant nuclear genomes is in large part caused by differences in accumulation of repetitive DNA. This makes repetitive DNA of great interest for studying the molecular mechanisms shaping architecture and function of complex plant genomes. However, due to methodological constraints of conventional cloning and sequencing, a global description of repeat composition is available for only a very limited number of higher plants. In order to provide further data required for investigating evolutionary patterns of repeated DNA within and between species, we used a novel approach based on massive parallel sequencing which allowed a comprehensive repeat characterization in our model species, garden pea (Pisum sativum). RESULTS: Analysis of 33.3 Mb sequence data resulted in quantification and partial sequence reconstruction of major repeat families occurring in the pea genome with at least thousands of copies. Our results showed that the pea genome is dominated by LTR-retrotransposons, estimated at 140,000 copies/1C. Ty3/gypsy elements are less diverse and accumulated to higher copy numbers than Ty1/copia. This is in part due to a large population of Ogre-like retrotransposons which alone make up over 20% of the genome. In addition to numerous types of mobile elements, we have discovered a set of novel satellite repeats and two additional variants of telomeric sequences. Comparative genome analysis revealed that there are only a few repeat sequences conserved between pea and soybean genomes. On the other hand, all major families of pea mobile elements are well represented in M. truncatula. CONCLUSION: We have demonstrated that even in a species with a relatively large genome like pea, where a single 454-sequencing run provided only 0.77% coverage, the generated sequences were sufficient to reconstruct and analyze major repeat families corresponding to a total of 35-48% of the genome. These data provide a starting point for further investigations of legume plant genomes based on their global comparative analysis and for the development of more sophisticated approaches for data mining.

SUBMITTER: Macas J

PROVIDER: S-EPMC2206039 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature

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Repetitive DNA in the pea (Pisum sativum L.) genome: comprehensive characterization using 454 sequencing and comparison to soybean and Medicago truncatula.

Macas Jirí J Neumann Pavel P Navrátilová Alice A

BMC genomics 20071121

<h4>Background</h4>Extraordinary size variation of higher plant nuclear genomes is in large part caused by differences in accumulation of repetitive DNA. This makes repetitive DNA of great interest for studying the molecular mechanisms shaping architecture and function of complex plant genomes. However, due to methodological constraints of conventional cloning and sequencing, a global description of repeat composition is available for only a very limited number of higher plants. In order to prov ...[more]

PMID: 18031571

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Project description:BackgroundProanthocyanidins (PAs) accumulate in the seeds, fruits and leaves of various plant species including the seed coats of pea (Pisum sativum), an important food crop. PAs have been implicated in human health, but molecular and biochemical characterization of pea PA biosynthesis has not been established to date, and detailed pea PA chemical composition has not been extensively studied.ResultsPAs were localized to the ground parenchyma and epidermal cells of pea seed coats. Chemical analyses of PAs from seeds of three pea cultivars demonstrated cultivar variation in PA composition. 'Courier' and 'Solido' PAs were primarily prodelphinidin-types, whereas the PAs from 'LAN3017' were mainly the procyanidin-type. The mean degree of polymerization of 'LAN3017' PAs was also higher than those from 'Courier' and 'Solido'. Next-generation sequencing of 'Courier' seed coat cDNA produced a seed coat-specific transcriptome. Three cDNAs encoding anthocyanidin reductase (PsANR), leucoanthocyanidin reductase (PsLAR), and dihydroflavonol reductase (PsDFR) were isolated. PsANR and PsLAR transcripts were most abundant earlier in seed coat development. This was followed by maximum PA accumulation in the seed coat. Recombinant PsANR enzyme efficiently synthesized all three cis-flavan-3-ols (gallocatechin, catechin, and afzalechin) with satisfactory kinetic properties. The synthesis rate of trans-flavan-3-ol by co-incubation of PsLAR and PsDFR was comparable to cis-flavan-3-ol synthesis rate by PsANR. Despite the competent PsLAR activity in vitro, expression of PsLAR driven by the Arabidopsis ANR promoter in wild-type and anr knock-out Arabidopsis backgrounds did not result in PA synthesis.ConclusionSignificant variation in seed coat PA composition was found within the pea cultivars, making pea an ideal system to explore PA biosynthesis. PsANR and PsLAR transcript profiles, PA localization, and PA accumulation patterns suggest that a pool of PA subunits are produced in specific seed coat cells early in development to be used as substrates for polymerization into PAs. Biochemically competent recombinant PsANR and PsLAR activities were consistent with the pea seed coat PA profile composed of both cis- and trans-flavan-3-ols. Since the expression of PsLAR in Arabidopsis did not alter the PA subunit profile (which is only comprised of cis-flavan-3-ols), it necessitates further investigation of in planta metabolic flux through PsLAR.

Project description:The genome sequences of several legume species are now available allowing the comparison of the nitrogen (N) transporter inventories with non-legume species. A survey of the genes encoding inorganic N transporters and the sensing and assimilatory families in pea, revealed similar numbers of genes encoding the primary N assimilatory enzymes to those in other types of plants. Interestingly, we find that pea and Medicago truncatula have fewer members of the NRT2 nitrate transporter family. We suggest that this difference may result from a decreased dependency on soil nitrate acquisition, as legumes have the capacity to derive N from a symbiotic relationship with diazotrophs. Comparison with M. truncatula, indicates that only one of three NRT2s in pea is likely to be functional, possibly indicating less N uptake before nodule formation and N-fixation starts. Pea seeds are large, containing generous amounts of N-rich storage proteins providing a reserve that helps seedling establishment and this may also explain why fewer high affinity nitrate transporters are required. The capacity for nitrate accumulation in the vacuole is another component of assimilation, as it can provide a storage reservoir that supplies the plant when soil N is depleted. Comparing published pea tissue nitrate concentrations with other plants, we find that there is less accumulation of nitrate, even in non-nodulated plants, and that suggests a lower capacity for vacuolar storage. The long-distance transported form of organic N in the phloem is known to be specialized in legumes, with increased amounts of organic N molecules transported, like ureides, allantoin, asparagine and amides in pea. We suggest that, in general, the lower tissue and phloem nitrate levels compared with non-legumes may also result in less requirement for high affinity nitrate transporters. The pattern of N transporter and assimilatory enzyme distribution in pea is discussed and compared with non-legumes with the aim of identifying future breeding targets.

Dataset Information

Repetitive DNA in the pea (Pisum sativum L.) genome: comprehensive characterization using 454 sequencing and comparison to soybean and Medicago truncatula.

Publications

Repetitive DNA in the pea (Pisum sativum L.) genome: comprehensive characterization using 454 sequencing and comparison to soybean and Medicago truncatula.

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