Proteome Profiling of Flax (<i>Linum usitatissimum</i>) Seed: Characterization of Functional Metabolic Pathways Operating during Seed Development

Flax (Linum usitatissimum L.) seeds
are an important
source of food and feed due to the presence of various health promoting
compounds, making it a nutritionally and economically important plant.
An in-depth analysis of the proteome of developing flax seed is expected
to provide significant information with respect to the regulation
and accumulation of such storage compounds. Therefore, a proteomic
analysis of seven seed developmental stages (4, 8, 12, 16, 22, 30,
and 48 days after anthesis) in a flax variety, NL-97 was carried out
using a combination of 1D-SDS-PAGE and LC-MSE methods.
A total 1716 proteins were identified and their functional annotation
revealed that a majority of them were involved in primary metabolism,
protein destination, storage and energy. Three carbon assimilatory
pathways appeared to operate in flax seeds. Reverse transcription
quantitative PCR of selected 19 genes was carried out to understand
their roles during seed development. Besides storage proteins, methionine
synthase, RuBisCO and S-adenosylmethionine synthetase
were highly expressed transcripts, highlighting their importance in
flax seed development. Further, the identified proteins were mapped
onto developmental seed specific expressed sequence tag (EST) libraries
of flax to obtain transcriptional evidence and 81% of them had detectable
expression at the mRNA level. This study provides new insights into
the complex seed developmental processes operating in flax.