Roti nylon membrane

For isolation of nucleic acids, cells were harvested by centrifugation at 1,100 x g, 4°C for 6 min. Genomic DNA was extracted using the DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) according to manufacturer's protocol or CTAB buffer (2% cetyltrimethylammonium bromide, 100 mM Tris-HCl, pH 8) followed by phenol/chloroform/isoamyl alcohol extraction (25:24:1, Carl Roth GmbH, Mannheim, Germany). DNAs were digested by restriction enzymes and separated on 0.8% agarose gels set up in TPE-buffer (89 mM Tris-phosphate, 2 mM Na 2 EDTA). Total cellular RNA was extracted by using the TRI reagent (Sigma-Aldrich, Saint Louis, USA), according to the manufacturer's instructions. RNAs were separated on 1% denaturing formaldehyde agarose gels. After separation nucleic acids were transferred to Roti Nylon + membrane (Roth, Karlsruhe, Germany), followed by UV light cross-linking (UV Crosslinker, UVC 500, Hoefer Inc., San Francisco, USA). Diglabeled probes were synthesized by PCR from total DNA or cloned cDNA (psbA) by using primers denoted in Supplemental Table S2. Hybridizations and detection of diglabeled probes were performed using standard methods.

Total RNA from Chlamydomonas was extracted by using the TRI reagent (Sigma). For Northern blot, total RNA was separated on denaturing formaldehyde agarose gels (1% or 2%), then transferred to Roti Nylon + membrane (Roth, www.roth.com), followed by UV light cross-linking (UV Crosslinker, UVC 500, Hoefer, www.hoefer.com). Dig-labelled probes were synthesized by PCR using dig-dNTP. Hybridizations and detection of dig-labelled probes were as described by (Sambrook and Russel, 2001) . RLM-RACE was performed using the Generacer kit (Invitrogen, www.lifetechnologies.com) according to the manufacturer's instruction, with primer Cr petG RLM rev.