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bioRxiv · 10.1101/2020.10.20.346734

nMAT3 is an essential maturase splicing factor required for holo-complex I biogenesis and embryo-development in Arabidopsis thaliana plants

Shevtsov-Tal, S.·Best, C.·Matan, R.·Chandran, S. A.·Brown, G. G.·Ostersetzer-Biran, O.
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Abstract

Group II introns are large catalytic RNAs that are particularly prevalent in the organelles of terrestrial plants. In angiosperm mitochondria, group II introns reside in the coding-regions of many critical genes, and their excision is essential for respiratory-mediated functions. Canonical group II introns are self-splicing and mobile genetic elements, consisting of the catalytic intron-RNA and its cognate intron-encoded endonuclease factor (i.e. maturase, Pfam-PF01348). Plant organellar introns are extremely degenerate, and lack many regions that are critical for splicing, including their related maturase-ORFs. The high degeneracy of plant mitochondrial introns was accompanied during evolution by the acquisition of host-acting protein cofactors. These include several nuclear encoded maturases (nMATs) and various other splicing-cofactors that belong to a diverse set of RNA-binding families, e.g. RNA helicases (Pfam-PF00910), Mitochondrial Transcription Termination Factors (mTERF, Pfam-PF02536), Plant Organelle RNA Recognition (PORR, Pfam-PF11955), and Pentatricopeptide repeat (PPR, Pfam-PF13812) proteins. Previously, we established the roles of MatR and three nuclear-maturases, nMAT1, nMAT2, and nMAT4, in the splicing of different subsets of mitochondrial introns in Arabidopsis. The function of nMAT3 (AT5G04050) was found to be essential during early embryogenesis. Using a modified embryo-rescue method, we show that nMAT3-knockout plants are strongly affected in the splicing of nad1 introns i1, i3 and i4 in Arabidopsis mitochondria. The embryo-defect phenotype is tightly associated with complex I biogenesis defects. Functional complementation of nMAT3 restored the splicing defects and altered embryogenesis phenotypes associated with the nmat3 mutant-line.

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Shevtsov-Tal, S., Best, C., Matan, R., Chandran, S. A., Brown, G. G., Ostersetzer-Biran, O.. 2020-10-21. nMAT3 is an essential maturase splicing factor required for holo-complex I biogenesis and embryo-development in Arabidopsis thaliana plants. https://doi.org/10.1101/2020.10.20.346734

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