Phylotranscriptomic Analyses of Mycoheterotrophic Monocots Show a Continuum of Convergent Evolutionary Changes in Expressed Nuclear Genes From Three Independent Nonphotosynthetic Lineages

Prakash Raj Timilsena, Craig F. Barrett, Alma Piñeyro-Nelson, Eric K. Wafula, Saravanaraj Ayyampalayam, Joel R. McNeal, Tomohisa Yukawa, Thomas J. Givnish, Sean W. Graham, J. Chris Pires, Jerrold I. Davis, Cécile Ané, Dennis W. Stevenson, Jim Leebens-Mack, Esteban Martínez-Salas, Elena R. Álvarez-Buylla, Claude W. dePamphilis

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Mycoheterotrophy is an alternative nutritional strategy whereby plants obtain sugars and other nutrients from soil fungi. Mycoheterotrophy and associated loss of photosynthesis have evolved repeatedly in plants, particularly in monocots. Although reductive evolution of plastomes in mycoheterotrophs is well documented, the dynamics of nuclear genome evolution remains largely unknown. Transcriptome datasets were generated from four mycoheterotrophs in three families (Orchidaceae, Burmanniaceae, Triuridaceae) and related green plants and used for phylogenomic analyses to resolve relationships among the mycoheterotrophs, their relatives, and representatives across the monocots. Phylogenetic trees based on 602 genes were mostly congruent with plastome phylogenies, except for an Asparagales + Liliales clade inferred in the nuclear trees. Reduction and loss of chlorophyll synthesis and photosynthetic gene expression and relaxation of purifying selection on retained genes were progressive, with greater loss in older nonphotosynthetic lineages. One hundred seventy-four of 1375 plant benchmark universally conserved orthologous genes were undetected in any mycoheterotroph transcriptome or the genome of the mycoheterotrophic orchid Gastrodia but were expressed in green relatives, providing evidence for massively convergent gene loss in nonphotosynthetic lineages. We designate this set of deleted or undetected genes Missing in Mycoheterotrophs (MIM). MIM genes encode not only mainly photosynthetic or plastid membrane proteins but also a diverse set of plastid processes, genes of unknown function, mitochondrial, and cellular processes. Transcription of a photosystem II gene (psb29) in all lineages implies a nonphotosynthetic function for this and other genes retained in mycoheterotrophs. Nonphotosynthetic plants enable novel insights into gene function as well as gene expression shifts, gene loss, and convergence in nuclear genomes.

Original languageEnglish (US)
JournalGenome biology and evolution
Volume15
Issue number1
DOIs
StatePublished - Jan 4 2023

All Science Journal Classification (ASJC) codes

  • General Medicine

Fingerprint

Dive into the research topics of 'Phylotranscriptomic Analyses of Mycoheterotrophic Monocots Show a Continuum of Convergent Evolutionary Changes in Expressed Nuclear Genes From Three Independent Nonphotosynthetic Lineages'. Together they form a unique fingerprint.

Cite this