Characterization of Vegetative Incompatibility in Morchella importuna and Location of the Related-Genes by Bulk Segregant Analysis.

Hongmei Chai,Nan Tao,Yuanhao Ma,Weimin Chen,Ping Liu,Yongchang Zhao

doi:10.3389/fmicb.2022.828514

Abstract

Vegetative incompatibility (VI) is a widespread phenomenon developed in Morchella importuna, a species of ascomycete fungus that is cultivated on a rapidly expanding scale in China. Understanding the genetic bases of this nonself-recognition phenomenon is beneficial for resolving some problems that are associated with the production of this highly prized edible fungus, such as crossbreeding, strain classification, and pathogen transmission. VI is genetically controlled by het genes, organized in two different systems, namely allelic and nonallelic. These het genes have been well characterized in Podospora anserina and Neurospora crassa. In this work, putative het-homologs were identified in the genome of M. importuna, but their low allelic polymorphism in different vegetative compatibility groups (VCGs) suggested that VI in this fungus might not be regulated by these het genes. The progeny derived from vegetative compatible parents became a VCG, while the single-ascospore strains from vegetative incompatible parents were divided into four VCGs, and the interaction between the inter-group strains led to the formation of two types of barrages, viz., thin dark line and raised aggregate of hyphae. The Bulk Segregant Analysis confirmed that the genes mimpvic32 and mimpvic33 were linked to VI reactions in M. importuna; nevertheless, the formation of barrages also occurred between the pairs carrying the same allele of these two genes. In sum, the VI control system in M. importuna was complicated, and there were more other allelic or non-allelic VI-related genes.

Highlights

In filamentous ascomycete fungi, the self/nonself-recognition of conspecific individuals occurs during sexual and asexual phases in the life cycle
The wild ascocarp Zhao0001 of M. importuna was collected from the Yulong County (Yunnan Province, China), and the ascospore print was provided by Dr Zhao Qi (Kunming Institute of Botany, Academia Sinica)
The detected homolog GME2544 showed more than 70% identity to un-24◦R and un24PA, but the high sequence similarity was only limited to the residues of the first N-terminal ribonucleoside reductase domain (PF02867), with more difference at their C-terminal

Summary

Introduction

The self/nonself-recognition of conspecific individuals occurs during sexual and asexual phases in the life cycle. For N. crassa, in addition to nonallelic pinc/het-c, and het-6/un-24, the allelic mating-type idiomorph is involved in incompatibility reaction; the expression of a gene named tol has been postulated to allow the coexistence of opposite mating-type nuclei during the sexual reproductive phase (Daskalov et al, 2017). The majority of these het genes characterize a protein containing a HET domain (Pfam06985), with approximately 150 amino acids (Espagne et al, 2002; Zhao et al, 2015), which plays a fundamental role as the mediator of VI-associated programmed cell death (PCD)

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