Gene expression levels of the Arabidopsis nuclear-coded elongation factor Gs. The Arabidopsis genome encodes for a total of three elongation factor Gs, including, SCO1 and two predicted mitochondrial-targeted EF-Gs. Transcript levels of SCO1 are highest in cotyledon tissue, with reduced levels in adult leaves. At1g45332 and At2g45030 transcript levels are highly reduced compared to SCO1 and remain constant between cotyledon and adult tissues. If these two EF-Gs are dual-targeted, they may be able to aid or compensate for the impaired activity of SCO1 in sco1-1 and sco1-4.