MRP3 is a sex determining gene in the diatom Pseudo-nitzschia multistriata

Monia T Russo,Filomena Romano,Marina Montresor,Carmen Minucci,Elio Biffali,Remo Sanges,Pasquale De Luca,Konstantinos Anestis,Laura Entrambasaguas,Maria I Ferrante,Wim Vyverman,Laura Vitale,Neri Fattorini

doi:10.1038/s41467-018-07496-0

Abstract

A broad diversity of sex-determining systems has evolved in eukaryotes. However, information on the mechanisms of sex determination for unicellular microalgae is limited, including for diatoms, key-players of ocean food webs. Here we report the identification of a mating type (MT) determining gene for the diatom Pseudo-nitzschia multistriata. By comparing the expression profile of the two MTs, we find five MT-biased genes, of which one, MRP3, is expressed exclusively in MT+ strains in a monoallelic manner. A short tandem repeat of specific length in the region upstream of MRP3 is consistently present in MT+ and absent in MT− strains. MRP3 overexpression in an MT− strain induces sex reversal: the transgenic MT− can mate with another MT− strain and displays altered regulation of the other MT-biased genes, indicating that they lie downstream. Our data show that a relatively simple genetic program is involved in defining the MT in P. multistriata.

Highlights

A broad diversity of sex-determining systems has evolved in eukaryotes
We report the identification of a mating type determining gene in the marine planktonic diatom Pseudonitzschia multistriata
We found 35 differentially expressed genes (Supplementary Table 1), including 14 genes that were known to be induced during the early phases of P. multistriata sexual reproduction[29]

Summary

Introduction

A broad diversity of sex-determining systems has evolved in eukaryotes. information on the mechanisms of sex determination for unicellular microalgae is limited, including for diatoms, key-players of ocean food webs. We report the identification of a mating type (MT) determining gene for the diatom Pseudo-nitzschia multistriata. 1234567890():,; Sexual reproduction is an ancient and almost universal feature in eukaryotes[1,2], and many types of sex determination systems have evolved in different eukaryotic groups[3,4]. Many centric diatoms are homothallic, and within the same clonal culture some cells differentiate into eggs and sperms that can self-fertilize, while most pennate diatoms are heterothallic and isogamous, or physiologically anisogamous[14], and sex occurs only when cells of distinct mating type (MT+ and MT−) below SST get in contact[13] (Supplementary Fig. 1). We report the identification of a mating type determining gene in the marine planktonic diatom Pseudonitzschia multistriata. The relatively simple model emerging from our study shows that MT + is determined in strains < SST inheriting an active copy of the gene MRP3 that in turn controls expression of four other MTrelated genes

Methods

Results

Conclusion