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Research article - Peer-reviewed, 2022

Dependence on clade II bHLH transcription factors for nursing of haploid products by tapetal-like cells is conserved between moss sporangia and angiosperm anthers

Lopez-Obando, Mauricio; Landberg, Katarina; Sundberg, Eva; Thelander, Mattias;

Abstract

Clade II basic helix-loop-helix transcription factors (bHLH TFs) are essential for pollen production and tapetal nursing functions in angiosperm anthers. As pollen has been suggested to be related to bryophyte spores by descent, we characterized two Physcomitrium (Physcomitrella) patens clade II bHLH TFs (PpbHLH092 and PpbHLH098), to test if regulation of sporogenous cells and the nursing cells surrounding them is conserved between angiosperm anthers and bryophyte sporangia. We made CRISPR-Cas9 reporter and loss-of-function lines to address the function of PpbHLH092/098. We sectioned and analyzed WT and mutant sporophytes for a comprehensive stage-by-stage comparison of sporangium development. Spore precursors in the P. patens sporangium are surrounded by nursing cells showing striking similarities to tapetal cells in angiosperms. Moss clade II bHLH TFs are essential for the differentiation of these tapetal-like cells and for the production of functional spores. Clade II bHLH TFs provide a conserved role in controlling the sporophytic somatic cells surrounding and nursing the sporogenous cells in both moss sporangia and angiosperm anthers. This supports the hypothesis that such nursing functions in mosses and angiosperms, lineages separated by roughly 450 million years, are related by descent.

Keywords

basic helix-loop-helix; bryophytes; moss; Physcomitrium patens; sporangium; sporogenesis; tapetum; transcription factor

Published in

New Phytologist

2022, volume: 235, number: 2, pages: 718-731
Publisher: WILEY

Authors' information

Swedish University of Agricultural Sciences, Department of Plant Biology
Vedas Corporación de Investigación e Innovación
Swedish University of Agricultural Sciences, Department of Plant Biology
Swedish University of Agricultural Sciences, Department of Plant Biology
Swedish University of Agricultural Sciences, Department of Plant Biology

UKÄ Subject classification

Botany

Publication Identifiers

DOI: https://doi.org/10.1111/nph.17972

URI (permanent link to this page)

https://res.slu.se/id/publ/115964