Abstract

Peanuts (Arachis hypogaea L.) are an important oilseed crop, containing high contents of protein and fatty acids (FA). The major components of FA found in peanut oil are unsaturated FAs, including oleic acid (OA, C18:1) and linoleic acid (LOA, C18:2). Moreover, the high content of OA in peanut oil is beneficial for human health and long-term storage due to its antioxidant activity. However, the dynamic changes in proteomics related to OA accumulation during seed development still remain largely unexplored. In the present study, a comparative proteome analysis based on iTRAQ (isobaric Tags for Relative and Absolute Quantification) was performed to identify the critical candidate factors involved in OA formation. A total of 389 differentially expressed proteins (DEPs) were identified between high-oleate cultivar Kainong176 and low-oleate cultivar Kainong70. Among these DEPs, 201 and 188 proteins were upregulated and downregulated, respectively. In addition, these DEPs were categorized into biosynthesis pathways of unsaturated FAs at the early stage during the high-oleic peanut seed development, and several DEPs involved in lipid oxidation pathway were found at the stage of seed maturation. Meanwhile, 28 DEPs were sporadically distributed in distinct stages of seed formation, and their molecular functions were directly correlated to FA biosynthesis and degradation. Fortunately, the expression of FAB2 (stearoyl-acyl carrier protein desaturase), the rate-limiting enzyme in the upstream biosynthesis process of OA, was significantly increased in the early stage and then decreased in the late stage of seed development in the high-oleate cultivar Kainong176. Furthermore, real-time PCR verified the expression pattern of FAB2 at the mRNA level, which was consistent with its protein abundance. However, opposite results were found for the low-oleate cultivar Kainong70. Overall, the comparative proteome analysis provided valuable insight into the molecular dynamics of OA accumulation during peanut seed development.

Highlights

  • Arachis hypogaea L., an important branch of the legume species, is commonly known as the peanut or groundnut

  • We performed a comprehensive proteome analysis to identify the expression profile of proteins involved in the oleic acid (OA) synthesis pathway during seed development in high- and normal-oleic peanut varieties

  • A total of 28 differentially expressed proteins (DEPs) were identified to participate in the regulation of fatty acids (FA) biosynthesis and degradation (Table S3), such as KASI, KASII, FAB2, acetyl-coenzyme A (CoA) family proteins and LCAS family proteins

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Summary

Introduction

Arachis hypogaea L., an important branch of the legume species, is commonly known as the peanut or groundnut. Cultivated peanuts are going through an evolution event due to the hybridization of two diploid ancestor wild species, Arachis duranensis (AA type) and Arachis ipaenis (BB type), resulting in induction of spontaneous chromosome doubling and formation of an allopolyploid (AABB type genome, 2n = 4x = 40) [2]. Comparative karyotyping analysis illustrates that chromosome organization is highly conserved in the peanut and its two putative progenitors, in the B genome chromosomes. Recent comparative karyotyping has shown that multiple hybridization and chromosome integration events of A. ipaensis with diverse varieties of A. duranensis have probably occurred in the peanut derived from the two diploid ancestors [3]. The entire genomes of A. duranensis and A. ipaensis have been sequenced and analyzed, laying the first step in understanding the evolution of the tetraploid genomes in peanuts as well as facilitating studies on the genetics, breeding and gene function in peanuts [4,5]

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