High-throughput discovery of plastid genes causing albino phenotypes in ornamental chimeric plants

Abstract

Chimeric plants composed of green and albino tissues have great ornamental value. To unveil the functional genes responsible for albino phenotypes in chimeric plants, we inspected the complete plastid genomes (plastomes) in green and albino leaf tissues from 23 ornamental chimeric plants belonging to 20 species, including monocots, dicots, and gymnosperms. In nine chimeric plants, plastomes were identical between green and albino tissues. Meanwhile, another 14 chimeric plants were heteroplasmic, showing a mutation between green and albino tissues. We identified 14 different point mutations in eight functional plastid genes related to plastid-encoded RNA polymerase (rpo) or photosystems which caused albinism in the chimeric plants. Among them, 12 were deleterious mutations in the target genes, in which early termination appeared due to small deletion-mediated frameshift or single nucleotide substitution. Another was single nucleotide substitution in an intron of the ycf3 and the other was a missense mutation in coding region of the rpoC2 gene. We inspected chlorophyll structure, protein functional model of the rpoC2, and expression levels of the related genes in green and albino tissues of Reynoutria japonica. A single amino acid change, histidine-to-proline substitution, in the rpoC2 protein may destabilize the peripheral helix of plastid-encoded RNA polymerase, impairing the biosynthesis of the photosynthesis system in the albino tissue of R. japonica chimera plant.

Acknowledgements

We thank Hantaek botanical garden, Seoul National University Arboretum, Medicinal Plant Garden of college of Pharmacy of Seoul National University for kindly provide the chimera materials; Minyoung Lee, Seonheui jeong Yonghyeok Jeong for their help to assembly of the plastomes. This work was supported by the Bio & Medical Technology Development Program of the NRF, MSIP, Republic of Korea (grant no. NRF-2015M3A9A5030733) and grants from the Nuclear R&D Program of the Ministry of Science and ICT (MSIT) and the research program of KAERI, Republic of Korea.

Author contributions

J.-H.J., H.-S.P., and T.-J.Y. designed the research. T.J.L, J.H.K, H.-Y.K, S.H.K, and J.-B.K provided the chimeric plant samples. J.-H.J., W.C., J.K., Y.S.P, and Y.L. assembled the chloroplast genomes of chimeric plants and conducted comparative genome analysis. J.-H.J. and H.J.K. designed the primers and performed the qRT-PCR. H.J.K. and J.-Y.S. performed the RpoC2 protein modeling. H.-S.P., W.C., and S.-H.K. measured the chlorophyll contents and performed a TEM analysis. H.-S.P., W.C., Y.L., J.-H.J. and T.-J.Y. wrote the manuscript, and H.-S.P., H.J.K., J.-Y.S., J.Y.P., G.J., N.-C.P., and T.-J.Y. revised the manuscript.

Data availability

Accession numbers: All sequence data used in this study have been deposited in the NCBI Nucleotide Database (Table S1). The Arabidopsis ACTIN1 sequence (NC_003071) and the chloroplast genome sequence of F. tataricum (NC_027161) were retrieved from GenBank.

Conflict interest

The authors declare no competing interests.

Supplementary data

Supplementary data is available at Horticulture Research online.

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