[1] Joint BioEnergy Inst, Feedstocks Div, Emeryville, CA 94608 USA
[2] Lawrence Berkeley Natl Lab, Phys Biosci Div, Emeryville, CA 94608 USA
[3] Univ Copenhagen, Villum Kann Rasmussen Ctr Proact Plants, Dept Plant Biol & Biotechnol, Fac Life Sci, DK-1871 Copenhagen, Denmark