Table 1.

Sizes of the four expansin families in different plants

Species	EXPA	EXPB	EXLA	EXLB
Last common ancestor	12	2	1	2
Arabidopsis	26	6	3	1
Poplar	27	2	2	4
Rice	34	19	4	1

The number of genes in each family is listed for the three plant species whose genomes have been sequenced. The number of genes in the last common ancestor of monocots and eudicots was estimated from an analysis of the rice and Arabidopsis genomes [7]. Numbers for poplar do not include partial gene fragments and should be taken as minimum estimates given that its genome is incompletely sequenced. EXPA, α-expansin; EXPB, β-expansin; EXLA, expansin-like A; EXLB, expansin-like B.