Fig. 4. ERL2 is haploinsufficient to maintain integument growth. (A,B) Transverse (horizontal) sections of Arabidopsis ovules at anthesis. (A) er-105 erl1-2/+ erl2-1 has a fully encased and developed embryo sac. (B) er-105 erl1-2 erl2-1/+ ovule has shorter integuments, protruding nucellus with no observable embryo sac. (C) Mean cell area (±s.e.m.) of the outer integument cells of wild type and er-105 erl1-2 erl2-1/+ (n=25, Student's t-test, P=0.331). (D) Cell number (±s.e.m.) in epidermis of ovules (stage 1-II) and the outer layer of the outer integument (stage 2-III, 3-III and 4-I) of wild-type and er-family mutant ovules at the indicated stages (n=25). Asterisks indicate a significant difference from the respective wild type within each stage using Student's t-test (P=0.01). At stage 3-III, a decrease in the number of cells in the outer integument is detected between wild type and er-family mutants. By stage 4-II, the number of cells in the outer integument is dramatically reduced compared with wild type. (E) Real-time RT-PCR analysis of selected cyclins in stage 12 carpels (left) and stage 3-II ovules (right). Loss of ER-family function results in a disruption of cyclin gene expression. Scale bars: 20 µm.