Gene expression differences among three Neurospora species reveal genes required for sexual reproduction in Neurospora crassa.
Nina A Lehr, Zheng Wang, Ning Li, David A Hewitt, Francesc López-Giráldez, Frances Trail, Jeffrey P Townsend
Author Information
Nina A Lehr: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.
Zheng Wang: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America; Department of Biostatistics, Yale University, New Haven, Connecticut, United States of America.
Ning Li: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.
David A Hewitt: Department of Botany, Academy of Natural Sciences, Philadelphia, Pennsylvania, United States of America; Wagner Free Institute of Science, Philadelphia, Pennsylvania, United States of America.
Francesc López-Giráldez: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.
Frances Trail: Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America; Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan, United States of America.
Jeffrey P Townsend: Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America; Department of Biostatistics, Yale University, New Haven, Connecticut, United States of America; Program in Computational Biology and Bioinformatics, Yale University, New Haven, Connecticut, United States of America; Program in Microbiology, Yale University, New Haven, Connecticut, United States of America.
Many fungi form complex three-dimensional fruiting bodies, within which the meiotic machinery for sexual spore production has been considered to be largely conserved over evolutionary time. Indeed, much of what we know about meiosis in plant and animal taxa has been deeply informed by studies of meiosis in Saccharomyces and Neurospora. Nevertheless, the genetic basis of fruiting body development and its regulation in relation to meiosis in fungi is barely known, even within the best studied multicellular fungal model Neurospora crassa. We characterized morphological development and genome-wide transcriptomics in the closely related species Neurospora crassa, Neurospora tetrasperma, and Neurospora discreta, across eight stages of sexual development. Despite diverse life histories within the genus, all three species produce vase-shaped perithecia. Transcriptome sequencing provided gene expression levels of orthologous genes among all three species. Expression of key meiosis genes and sporulation genes corresponded to known phenotypic and developmental differences among these Neurospora species during sexual development. We assembled a list of genes putatively relevant to the recent evolution of fruiting body development by sorting genes whose relative expression across developmental stages increased more in N. crassa relative to the other species. Then, in N. crassa, we characterized the phenotypes of fruiting bodies arising from crosses of homozygous knockout strains of the top genes. Eight N. crassa genes were found to be critical for the successful formation of perithecia. The absence of these genes in these crosses resulted in either no perithecium formation or in arrested development at an early stage. Our results provide insight into the genetic basis of Neurospora sexual reproduction, which is also of great importance with regard to other multicellular ascomycetes, including perithecium-forming pathogens, such as Claviceps purpurea, Ophiostoma ulmi, and Glomerella graminicola.
