Universality of the Phytophthora mating hormones and diversity of their production profile

Tomohiko Tomura,Ryo Murata,Shylaja D Molli,Makoto Ojika

doi:10.1038/s41598-017-05380-3

Abstract

Sexual reproduction of the plant pest Phytophthora is regulated by two mating hormones α1 and α2, which are acyclic oxygenated diterpenes first isolated from P. nicotianae A1 and A2 mating types, respectively. A previous report suggested the universality of these factors within this genus. To confirm this concept, we investigated 80 strains (19 species) of Phytophthora and a related genus, not only for the responsiveness to mating hormones but also for their productivity. The results indicated that among the 55 heterothallic strains, 24 (44%) responded to a mating hormone and 40 (73%) produced one or both hormones. These findings demonstrate the interspecies universality of mating hormones within the genus Phytophthora. Hormone productivity was found to be highly diverse and dependent on the strains used. Although the A2 mating type has been regarded as the α2 producer, 19 (59%) of the 32 A2-type strains produced both the hormones and two A2-type strains exclusively produced α1 in high yields. These results indicate that hormone biosynthesis in Phytophthora is universal but highly diverse and complex, and varies with culture conditions, providing us valuable information for future studies on the mechanism of mating hormone biosynthesis of Phytophthora.

Highlights

The genus Phytophthora represents a group of filamentous fungus-like oomycetes and includes more than 100 species, most of which are deleterious to a broad range of economically and ecologically important plant species[1, 2]
The A1 mating-type strains are those that produce α1 and/or respond to α2 produced by A2), whereas the A2 strains are those that produce α2 and/ or respond to α1
The A1,A2-type strains were defined by Ko10 as those that either produce both the mating hormones or respond to both hormones, it is a hypothetical type without examples

Summary

Introduction

The genus Phytophthora represents a group of filamentous fungus-like oomycetes and includes more than 100 species, most of which are deleterious to a broad range of economically and ecologically important plant species[1, 2]. After many years of efforts, the mating hormones α1 and α2 were identified from an A1 mating-type strain of P. nicotianae in 20056 and from a strain of the counter A2 mating type in 20117, respectively Both hormones, characterized as new acyclic diterpenes, were found to be biosynthesized from phytol by incorporation experiments (Fig. 1)[7]. It was reported half a century ago that most interspecies pairing between heterothallic species of A1 and A2 types resulted in sexual reproduction[3]. This was achieved using 80 strains (19 species) of Phytophthora and the related genus Halophytophthora (comprising halophilic members of Phytophthora that predominantly inhabit brackish water mangroves[8])

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