Selective and multiple silencing of Lhcbm genes using artificial miRNAs: prospects for optimizing photosynthetic yield

Paola Ferrante1, Giulia Bonente2, Giovanni Giuliano1, and Roberto Bassi2

1) ENEA, Casaccia Res. Ctr., Rome, Italy 2) Università degli Studi di Verona, Verona, Italy

Chlamydomonas reinhardtii is currently used in molecular farming and biological hydrogen production. However, its solar conversion efficiency is strongly limited by photoinhibitory phenomena occurring at high light intensities. Size reduction of the functional antennas is a possible way to overcome this bottleneck. We employed artificial microRNA (amiRNA) technology to silence two genes (Lhcbm2 and Lhcbm8) of the major light-harvesting complex of photosystem II. Real Time RT PCR analyses show that the two different amiRNA chosen for the silencing of the Lhcbm2 gene are able to specifically decrease its mRNA levels. Moreover an amiRNA designed to silence both the Lhcbm2 and Lhcbm8 genes was effective in reducing the amount of both mRNAs. Silenced Lhcbm 2+8 lines showed high Chla/Chlb ratio, suggesting that they have a reduced functional PSII antenna. They also showed altered amounts of xantophylls and altered beta-carotene/xantophyll ratios with respect to the wild type. These data suggest that the amiRNA technology has good potential to triggering specific and multiple silencing of proteins encoded by multigene families. Acknowledgments: Supported by grants of the Italian Ministries of Research and Agriculture to GG and RB. We thank A. Molnar for advice on amiRNA design and use.

e-mail address of presenting author: paola.ferrante@enea.it

web site: http://www.enea.it/