Map-based cloning of <i>ABO8</i>.

<p>A. <i>ABO8</i> was mapped to chromosome 4. A point mutation from G447 to A447 (counting from the first putative ATG in <i>AT4G11690</i>) was identified in <i>abo8-1</i>. A T-DNA insertion line SALK_025470 (<i>abo8-2</i>, T-DNA is inserted in position +358) was obtained from the Arabidopsis Biological Resource Center. B. RT-PCR analysis of <i>ABO8</i> transcripts in <i>abo8-2</i> using primers flanking the T-DNA insertion. Expression of the <i>ACTIN2</i> gene was used as control. C. The protein structure of ABO8. SP: signal peptide; PPR: pentatricopeptide repeat. D. Genetic analysis of <i>abo8-1</i> and <i>abo8-2</i> for sensitivity of root growth to ABA. Four-day-old seedlings grown on MS medium were transferred to MS medium containing 0 or 30 µM ABA. <i>abo8-1 abo8-2</i>: F1 seedlings of <i>abo8-1</i> crossed with <i>abo8-2</i>. Bars = 5 mm. E. Seed germination greening analysis of <i>abo8-1</i> complemented with an <i>ABO8</i> promoter driving <i>ABO8</i> cDNA fused with <i>GFP</i> cDNA (<i>ProABO8:ABO8-GFP</i>) on MS medium containing 0.0 or 0.3 µM ABA. Bars = 5 mm. F. Statistical analysis of seed germination greening rate of the complemented <i>abo8-1</i> in (E). Three independent experiments were done, each with three replicates (from three different plates). About 24 seeds were counted for each plate. Values are means ±SE, n = 3. **: P<0.01. G. Roots of <i>abo8-1</i> complemented with <i>ProABO8:ABO8-GFP</i>. Four-day-old seedlings were transferred to MS medium containing 0 or 30 µM ABA. Bars = 5 mm. H. Statistical analysis of root length in (G). Root length is expressed relative to that of the wild type or <i>abo8-1</i> without ABA. Three independent experiments were done with similar results, each with three biological repeats. Five roots from one plate were measured for each repeat. Values are means ±SE, n = 3. **: P<0.01.