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Title: Proteomic analysis of Pigeonpea (cajanus cajan) seeds reveals the accumulation of numerous stress-related proteins

Author
item Krishnan, Hari
item Natarajan, Savithiry - Savi
item Oehrle, Nathan
item Garrett, Wesley
item DARWISH, OMAR - Towson University

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2017
Publication Date: 5/22/2017
Citation: Krishnan, H.B., Natarajan, S.S., Oehrle, N.W., Garrett, W.M., Darwish, O. 2017. Proteomic analysis of Pigeonpea (cajanus cajan) seeds reveals the accumulation of numerous stress-related proteins. Journal of Agricultural and Food Chemistry. 65(23):4572-4581. doi: 10.1021/acs.jafc.7b00998.

Interpretive Summary: Legumes are an inexpensive source of highly nutritious and well-balanced dietary protein. Pigeonpea is an important legume crop commonly grown in semi-arid tropical regions of the world. Importantly, this crop is a major protein source for a large section of the human population and is vital to for food security in many developing countries. Unlike soybean, very little information is available on the seed storage proteins of pigeonpea, an important component that impacts nutritional value of the seeds. In this study we have performed a detailed analysis of pigeonpea seed proteins utilizing both standard protein separation techniques and the more recent protein fragment sequencing technologies. Recent genome sequencing projects have shown that a large number of pigeonpea genes show significant similarity with soybean genes even though these two legumes are in separate ancestral lineages that moved apart about 20-30 million years ago. This close similarity between the two plants allows us to utilize pigeonpea genes that control the composition of their seed storage proteins in soybean seed composition improvement strategies. The ability to utilize natural variation in seed storage proteins to improve US soybeans will greatly advance our efforts in this endeavor.

Technical Abstract: Pigeonpea is one of the major sources of dietary protein for more than a billion people living in South Asia. This hardy legume is often grown in low-input and risk-prone marginal environments. Considerable research effort has been devoted by a global research consortium to develop genomic resources for the improvement of this legume crop. These efforts have resulted in the elucidation of the complete genome sequence of pigeonpea. Despite these developments, little is known about seed proteome of this important crop. Here, we report the proteome of pigeonpea seed. To enable the isolation of maximum number of seed proteins, including those that are present in very low amounts, three different protein fractions were obtained by employing different extraction media. High-resolution two-dimensional (2-D) electrophoresis followed by MALDI-TOF-TOF-MS/MS analysis of these protein fractions resulted in the identification of 373 pigeonpea seed proteins. Consistent with the reported high degree of synteny between pigeonpea and soybean genome, a large number of pigeonpea seed proteins exhibited significant amino acid homology with soybean seed proteins. Our proteomic analysis identified a large number of proteins with a potential role in abiotic stress, presumably due to its adaptation to drought-prone environments. The availability of a pigeonpea seed proteome reference map should shed light on the roles of these identified proteins in various biological processes and facilitate the improvement of seed composition.