title: Gametophyte Development Needs Mitochondrial Coproporphyrinogen III Oxidase Function.
abstract: Tetrapyrrole biosynthesis is one of the most essential metabolic pathways in almost all organisms. Coproporphyrinogen III oxidase (CPO) catalyzes the conversion of coproporphyrinogen III into protoporphyrinogen IX in this pathway. Here, we report that mutation in the Arabidopsis (Arabidopsis thaliana) CPO-coding geneAt5g63290(AtHEMN1) adversely affects silique length, ovule number, and seed set.Athemn1mutant alleles were transmitted via both male and female gametes, but homozygous mutants were never recovered. Plants carryingAthemn1mutant alleles showed defects in gametophyte development, including nonviable pollen and embryo sacs with unfused polar nuclei. Improper differentiation of the central cell led to defects in endosperm development. Consequently, embryo development was arrested at the globular stage. The mutant phenotype was completely rescued by transgenic expression ofAtHEMN1Promoter and transcript analyses indicated thatAtHEMN1is expressed mainly in floral tissues and developing seeds. AtHEMN1-green fluorescent protein fusion protein was found targeted to mitochondria. Loss ofAtHEMN1function increased coproporphyrinogen III level and reduced protoporphyrinogen IX level, suggesting the impairment of tetrapyrrole biosynthesis. Blockage of tetrapyrrole biosynthesis in theAtHEMN1mutant led to increased reactive oxygen species (ROS) accumulation in anthers and embryo sacs, as evidenced by nitroblue tetrazolium staining. Our results suggest that the accumulated ROS disrupts mitochondrial function by altering their membrane polarity in floral tissues. This study highlights the role of mitochondrial ROS homeostasis in gametophyte and seed development and sheds new light on tetrapyrrole/heme biosynthesis in plant mitochondria.
authors.affiliation: Biotechnology Division, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., S.K.S., Y.S.).|Academy of Scientific and Innovative Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., Y.S.); and.|Indian Council of Agricultural Research-National Research Centre on Plant Biotechnology, New Delhi 110012, India (R.S., S.R.B.).
authors.forename: Pritu
authors.identifier: http://orcid.org/0000-0002-6360-7980
authors.initials: P
authors.lastname: Pratibha
authors.affiliation: Biotechnology Division, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., S.K.S., Y.S.).|Academy of Scientific and Innovative Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., Y.S.); and.|Indian Council of Agricultural Research-National Research Centre on Plant Biotechnology, New Delhi 110012, India (R.S., S.R.B.).
authors.forename: Sunil Kumar
authors.identifier: http://orcid.org/0000-0002-6234-0276
authors.initials: SK
authors.lastname: Singh
authors.affiliation: Biotechnology Division, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., S.K.S., Y.S.).|Academy of Scientific and Innovative Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., Y.S.); and.|Indian Council of Agricultural Research-National Research Centre on Plant Biotechnology, New Delhi 110012, India (R.S., S.R.B.).
authors.forename: Ramamurthy
authors.identifier: http://orcid.org/0000-0002-3875-6650
authors.initials: R
authors.lastname: Srinivasan
authors.affiliation: Biotechnology Division, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., S.K.S., Y.S.); srbhat@nrcpb.org sreenivasulu@ccmb.res.in.|Academy of Scientific and Innovative Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., Y.S.); and srbhat@nrcpb.org sreenivasulu@ccmb.res.in.|Indian Council of Agricultural Research-National Research Centre on Plant Biotechnology, New Delhi 110012, India (R.S., S.R.B.) srbhat@nrcpb.org sreenivasulu@ccmb.res.in.
authors.forename: Shripad Ramachandra
authors.identifier: http://orcid.org/0000-0002-8349-6691
authors.initials: SR
authors.lastname: Bhat
authors.affiliation: Biotechnology Division, Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., S.K.S., Y.S.); srbhat@nrcpb.org sreenivasulu@ccmb.res.in.|Academy of Scientific and Innovative Research-Institute of Himalayan Bioresource Technology, Palampur 176061, Himachal Pradesh, India (P.P., Y.S.); and srbhat@nrcpb.org sreenivasulu@ccmb.res.in.|Indian Council of Agricultural Research-National Research Centre on Plant Biotechnology, New Delhi 110012, India (R.S., S.R.B.) srbhat@nrcpb.org sreenivasulu@ccmb.res.in.
authors.forename: Yelam
authors.identifier: http://orcid.org/0000-0003-2610-3916
authors.initials: Y
authors.lastname: Sreenivasulu
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003304:Coproporphyrinogen Oxidase / Q000235:genetics / Q000378:metabolism*; D003305:Coproporphyrinogens / Q000378:metabolism; D056625:Endosperm / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D055993:Germ Cells, Plant / Q000254:growth & development / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D009154:Mutation; D056771:Ovule / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D003305:Coproporphyrinogens; D017382:Reactive Oxygen Species; C028026:coproporphyrinogen III; D003304:Coproporphyrinogen Oxidase