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Gene expression analysis of flax seed development.

Venglat P, Xiang D, Qiu S, Stone SL, Tibiche C, Cram D, Alting-Mees M, Nowak J, Cloutier S, Deyholos M, Bekkaoui F, Sharpe A, Wang E, Rowland G, Selvaraj G, Datla R - BMC Plant Biol. (2011)

Bottom Line: When compared with fully sequenced plant genomes, the flax unigenes resembled poplar and castor bean more than grape, sorghum, rice or Arabidopsis.We have developed a foundational database of expressed sequences and collection of plasmid clones that comprise even low-expressed genes such as those encoding transcription factors.Flax belongs to a taxonomic group of diverse plants and the large sequence database will allow for evolutionary studies as well.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Biotechnology Institute, NRC, 110 Gymnasium Place, Saskatoon, Saskatchewan, S7N 0W9, Canada.

ABSTRACT

Background: Flax, Linum usitatissimum L., is an important crop whose seed oil and stem fiber have multiple industrial applications. Flax seeds are also well-known for their nutritional attributes, viz., omega-3 fatty acids in the oil and lignans and mucilage from the seed coat. In spite of the importance of this crop, there are few molecular resources that can be utilized toward improving seed traits. Here, we describe flax embryo and seed development and generation of comprehensive genomic resources for the flax seed.

Results: We describe a large-scale generation and analysis of expressed sequences in various tissues. Collectively, the 13 libraries we have used provide a broad representation of genes active in developing embryos (globular, heart, torpedo, cotyledon and mature stages) seed coats (globular and torpedo stages) and endosperm (pooled globular to torpedo stages) and genes expressed in flowers, etiolated seedlings, leaves, and stem tissue. A total of 261,272 expressed sequence tags (EST) (GenBank accessions LIBEST_026995 to LIBEST_027011) were generated. These EST libraries included transcription factor genes that are typically expressed at low levels, indicating that the depth is adequate for in silico expression analysis. Assembly of the ESTs resulted in 30,640 unigenes and 82% of these could be identified on the basis of homology to known and hypothetical genes from other plants. When compared with fully sequenced plant genomes, the flax unigenes resembled poplar and castor bean more than grape, sorghum, rice or Arabidopsis. Nearly one-fifth of these (5,152) had no homologs in sequences reported for any organism, suggesting that this category represents genes that are likely unique to flax. Digital analyses revealed gene expression dynamics for the biosynthesis of a number of important seed constituents during seed development.

Conclusions: We have developed a foundational database of expressed sequences and collection of plasmid clones that comprise even low-expressed genes such as those encoding transcription factors. This has allowed us to delineate the spatio-temporal aspects of gene expression underlying the biosynthesis of a number of important seed constituents in flax. Flax belongs to a taxonomic group of diverse plants and the large sequence database will allow for evolutionary studies as well.

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Flax tissues used for cDNA library construction and EST analysis. (A) globular embryo; (B) heart embryo; (C) torpedo embryo; (D) cotyledon embryo; (E) mature embryo; (F) globular stage seed coat; (G) torpedo stage seed coat; (H) pooled endosperm from globular to torpedo stage seed; (I) etiolated seedlings; (J) stem; (K) stem peel "PS"; (L) leaves; and (M) mature flower.
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Figure 2: Flax tissues used for cDNA library construction and EST analysis. (A) globular embryo; (B) heart embryo; (C) torpedo embryo; (D) cotyledon embryo; (E) mature embryo; (F) globular stage seed coat; (G) torpedo stage seed coat; (H) pooled endosperm from globular to torpedo stage seed; (I) etiolated seedlings; (J) stem; (K) stem peel "PS"; (L) leaves; and (M) mature flower.

Mentions: Limited information is available regarding flax seed development, despite its economic importance. Since the seed is an economically important output of this crop, in this study, we performed a detailed analysis of embryogenesis and flax seed development. The flax seed consists of three major tissues: the diploid embryo and triploid endosperm as products of double fertilization, and the maternal seed coat tissue. Soon after fertilization, the seed is translucent and the embryo sac is upright within the integuments (Figure 1A). The developing embryo is anchored at the micropylar end of the embryo sac. The thick, clear and fragile integuments of the fertilized ovule differentiate into the thin, dark and protective seed coat during seed development. Observation during the dissection process revealed that the endosperm initials, which formed at fertilization, undergo divisions to form a cellularized endosperm by the globular embryo stage (Figure 1B and Figure 2H). The endosperm progressively increases in size up to the torpedo stage, after which time it begins to degenerate, presumably to make space for the rapidly elongating cotyledons and to provide nutritional support to the developing embryo. By the late cotyledon stage the majority of endosperm cells have been consumed, leaving a thin layer of endosperm on the inner wall of the seed coat of the maturing seed.


Gene expression analysis of flax seed development.

Venglat P, Xiang D, Qiu S, Stone SL, Tibiche C, Cram D, Alting-Mees M, Nowak J, Cloutier S, Deyholos M, Bekkaoui F, Sharpe A, Wang E, Rowland G, Selvaraj G, Datla R - BMC Plant Biol. (2011)

Flax tissues used for cDNA library construction and EST analysis. (A) globular embryo; (B) heart embryo; (C) torpedo embryo; (D) cotyledon embryo; (E) mature embryo; (F) globular stage seed coat; (G) torpedo stage seed coat; (H) pooled endosperm from globular to torpedo stage seed; (I) etiolated seedlings; (J) stem; (K) stem peel "PS"; (L) leaves; and (M) mature flower.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3107784&req=5

Figure 2: Flax tissues used for cDNA library construction and EST analysis. (A) globular embryo; (B) heart embryo; (C) torpedo embryo; (D) cotyledon embryo; (E) mature embryo; (F) globular stage seed coat; (G) torpedo stage seed coat; (H) pooled endosperm from globular to torpedo stage seed; (I) etiolated seedlings; (J) stem; (K) stem peel "PS"; (L) leaves; and (M) mature flower.
Mentions: Limited information is available regarding flax seed development, despite its economic importance. Since the seed is an economically important output of this crop, in this study, we performed a detailed analysis of embryogenesis and flax seed development. The flax seed consists of three major tissues: the diploid embryo and triploid endosperm as products of double fertilization, and the maternal seed coat tissue. Soon after fertilization, the seed is translucent and the embryo sac is upright within the integuments (Figure 1A). The developing embryo is anchored at the micropylar end of the embryo sac. The thick, clear and fragile integuments of the fertilized ovule differentiate into the thin, dark and protective seed coat during seed development. Observation during the dissection process revealed that the endosperm initials, which formed at fertilization, undergo divisions to form a cellularized endosperm by the globular embryo stage (Figure 1B and Figure 2H). The endosperm progressively increases in size up to the torpedo stage, after which time it begins to degenerate, presumably to make space for the rapidly elongating cotyledons and to provide nutritional support to the developing embryo. By the late cotyledon stage the majority of endosperm cells have been consumed, leaving a thin layer of endosperm on the inner wall of the seed coat of the maturing seed.

Bottom Line: When compared with fully sequenced plant genomes, the flax unigenes resembled poplar and castor bean more than grape, sorghum, rice or Arabidopsis.We have developed a foundational database of expressed sequences and collection of plasmid clones that comprise even low-expressed genes such as those encoding transcription factors.Flax belongs to a taxonomic group of diverse plants and the large sequence database will allow for evolutionary studies as well.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Biotechnology Institute, NRC, 110 Gymnasium Place, Saskatoon, Saskatchewan, S7N 0W9, Canada.

ABSTRACT

Background: Flax, Linum usitatissimum L., is an important crop whose seed oil and stem fiber have multiple industrial applications. Flax seeds are also well-known for their nutritional attributes, viz., omega-3 fatty acids in the oil and lignans and mucilage from the seed coat. In spite of the importance of this crop, there are few molecular resources that can be utilized toward improving seed traits. Here, we describe flax embryo and seed development and generation of comprehensive genomic resources for the flax seed.

Results: We describe a large-scale generation and analysis of expressed sequences in various tissues. Collectively, the 13 libraries we have used provide a broad representation of genes active in developing embryos (globular, heart, torpedo, cotyledon and mature stages) seed coats (globular and torpedo stages) and endosperm (pooled globular to torpedo stages) and genes expressed in flowers, etiolated seedlings, leaves, and stem tissue. A total of 261,272 expressed sequence tags (EST) (GenBank accessions LIBEST_026995 to LIBEST_027011) were generated. These EST libraries included transcription factor genes that are typically expressed at low levels, indicating that the depth is adequate for in silico expression analysis. Assembly of the ESTs resulted in 30,640 unigenes and 82% of these could be identified on the basis of homology to known and hypothetical genes from other plants. When compared with fully sequenced plant genomes, the flax unigenes resembled poplar and castor bean more than grape, sorghum, rice or Arabidopsis. Nearly one-fifth of these (5,152) had no homologs in sequences reported for any organism, suggesting that this category represents genes that are likely unique to flax. Digital analyses revealed gene expression dynamics for the biosynthesis of a number of important seed constituents during seed development.

Conclusions: We have developed a foundational database of expressed sequences and collection of plasmid clones that comprise even low-expressed genes such as those encoding transcription factors. This has allowed us to delineate the spatio-temporal aspects of gene expression underlying the biosynthesis of a number of important seed constituents in flax. Flax belongs to a taxonomic group of diverse plants and the large sequence database will allow for evolutionary studies as well.

Show MeSH
Related in: MedlinePlus