Abstract

Cytochrome P450 (CYP) catalyzes a wide variety of monooxygenation reactions in plant primary and secondary metabolisms. Land plants contain CYP703, belonging to the CYP71 clan, which catalyzes the biochemical pathway of fatty acid hydroxylation, especially in male reproductive tissues. Korean/Asian ginseng (Panax ginseng Meyer) has been regarded as one of important medicinal plant for a long time, however the molecular mechanism is less known on its development. In this study, we identified and characterized a CYP703A gene in P. ginseng (PgCYP703A4), regarding reproductive development. PgCYP703A4 shared a high-sequence identity (81–83%) with predicted amino acid as CYP703 in Dancus carota, Pistacia vera, and Camellia sinensis as well as 76% of amino acid sequence identity with reported CYP703 in Arabidopsis thaliana and 75% with Oryza sativa. Amino acid alignment and phylogenetic comparison of P. ginseng with higher plants and known A. thaliana members clearly distinguish the CYP703 members, each containing the AATDTS oxygen binding motif and PERH as a clade signature. The expression of PgCYP704B1 was only detected in P. ginseng flower buds, particularly in meiotic cells and the tapetum layer of developing anther, indicating the conserved role on male reproduction with At- and Os- CYP703. To acquire the clue of function, we transformed the PgCYP703A4 in A. thaliana. Independent overexpressing lines (PgCYP703A4ox) increased silique size and seed number, and altered the contents of fatty acids composition of cutin monomer in the siliques. Our results indicate that PgCYP703A4 is involved in fatty acid hydroxylation which affects cutin production and fruit size.

Highlights

  • The cytochrome P450 (CYP) superfamily of enzymes, which catalyze diverse substrates through oxygenation and hydroxylation reactions, are found in all organisms [1]

  • Analysis of the P. ginseng genome scaffold and coding sequence (CDS) revealed that P. ginseng contains two scaffold sequences with high similarity to CYP703

  • We concluded that the P. ginseng genome encodes just one PgCYP703 member, whereas the others are nonfunctional genes

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Summary

Introduction

The cytochrome P450 (CYP) superfamily of enzymes, which catalyze diverse substrates through oxygenation and hydroxylation reactions, are found in all organisms [1]. The diversification of land plant CYP families emerges during flowering plant evolution and specializes plant species with unique reactions [3]. The identification of CYP genes aids in understanding the evolution of various groups of enzymes and their conserved and diversified functions. The CYP703 gene family was found across the land plant taxa, suggesting that it encodes an essential function [4]. Land plants developed specialized cell layer to adapt to the environment, including cutin synthesis. As cutin cover in most plant organ of land plant, male reproductive organ of flowering plants is covered with a hydrophobic polymer barrier derived from fatty acids. Male reproduction is a complex and highly coordinated biological process that includes the development of the male reproductive organ: the stamen that contains the microspores and pollen. The study of male reproduction is important for increasing crop yield but for producing improved crops, such as superhybrid plants, through the use of male sterile lines [6]

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