A mitochondrial ADXR–ADX–P450 electron transport chain is essential for maternal gametophytic control of embryogenesis in Arabidopsis

BELLIDO, ANDRÉS MARTIN; DISTÉFANO, AYELÉN MARIANA; SETZES, NICOLÁS; CASCALLARES, MARÍA MILAGROS; OKLESTKOVA, JANA; NOVAK, ONDREJ; RAMIREZ, JAVIER ALBERTO; ZABALETA, EDUARDO J.; FIOL, DIEGO F.; PAGNUSSAT, GABRIELA C.

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2022 vol. 119

0027-8424

Mitochondrial adrenodoxins (ADXs) are small iron?sulfur proteinswith electron transfer properties. In animals, ADXs transfer electrons between an adrenodoxin reductase (ADXR) and mitochondrial P450s, which is crucial for steroidogenesis. Here we showthat a plant mitochondrial steroidogenic pathway, dependent onan ADXR?ADX?P450 shuttle, is essential for female gametogenesisand early embryogenesis through a maternal effect. The steroidprofile of maternal and gametophytic tissues of wild-type (WT)and adxr ovules revealed that homocastasterone is the main steroid present in WT gametophytes and that its levels are reduced inthe mutant ovules. The application of exogenous homocastasterone partially rescued adxr and P450 mutant phenotypes, indicating that gametophytic homocastasterone biosynthesis is affectedin the mutants and that a deficiency of this hormone causes thephenotypic alterations observed. These findings also suggest notonly a remarkable similarity between steroid biosynthetic pathways in plants and animals but also a common function duringsexual reproduction.