Figure 6.
Expression characteristics and auxin inducibility of CnAIP2pro-GUS in young seedlings and promotive effects of CnAIP2 on seedling root growth and lateral root initiation. A, Histochemical analyses conducted on young seedlings expressing CnAIP2pro-GUS. a to c, Seedlings at 2, 4, and 7 d after germination; d to f, GUS expression at the lateral root initiation sites; g, 4-d-old seedling treated with 1 µm 2,4-D overnight prior to X-gluc staining. Chlorophyll was removed by incubating seedlings in 95% ethanol overnight after X-gluc staining. Photographs are cropped at different magnifications to show proper details. B, Effect of auxins on CnAIP2-GUS expression of young seedlings. Activities of GUS were determined by the fluorometric assay conducted on 3-d-old seedlings incubated overnight (16 h) in one-half-strength MS liquid medium with various concentrations (µm) of auxins as indicated. Data represent means ± se of duplicate experiments. MU, Methylumbelliferone. C and D, Effects of CnAIP2 expression (CnAIP2-OE) on root length (C) and number of lateral roots (D) showing CnAIP2 transgenic seedlings versus wild-type (WT; control) seedlings after 1 week and 2 weeks at germination/growth conditions. Seeds were subjected to a 4-d moist-chilling treatment (4°C) on one-half-strength MS plates prior to transfer of plates to germination conditions. Data represent means ± sd of approximately 50 plants of wild-type or CnAIP2 transgenic plants. Asterisks indicate significant differences (**P < 0.001, *P < 0.05) from the wild type determined by Student’s t test.