Phylogenetic alignment (phyml/NJ) of the ABA receptor proteins in <i>Cuscuta australis</i> (4 receptors), <i>Arabidopsis thaliana</i> (14 receptors), <i>Solanum lycopersicum</i> (15 receptors), and <i>Oryza sativa</i> (12 receptors).

<p>The phylogenetic analysis was performed using the neighbor-joining algorithms of MEGA 5.2. The sequences of the 4 CaPYLs are highlighted in bold. Numbers above the branches indicate bootstrap support values of maximum likelihood no less than 75%.</p

<i>C</i>. <i>australis</i> seedlings are highly insensitive to ABA.

<p><i>C</i>. <i>australis</i> and tomato seeds were germinated on ½ MS plates, and when seedlings grew to 1 cm in length, they were transferred to liquid ½ MS medium containing different concentrations of ABA to grow for 5 more days. (<b>A</b>) A photograph of tomato (top) and <i>C</i>. <i>australis</i> seedlings (bottom) (Scale bar = 1cm). (<b>B</b>) The lengths of tomato hypocotyls and <i>C</i>. <i>australis</i> seedlings relative to those of the controls (without ABA). Results are presented as the mean ± SE (N = 10). Asterisks indicate significant differences between the respective control and treated groups determined by Student’s <i>t</i>-test (***, P < 0.001).</p

<i>C</i>. <i>australis</i> seedlings can take up ABA from the media.

<p><i>C</i>. <i>australis</i> and tomato seedlings were germinated and grown to about 1cm in length before they were transferred to 1/2 MS medium containing 50 μM of ABA or no ABA (indicated by ABA and C on the X-axis) and incubated for 24 h. Subsequently, seedlings were thoroughly rinsed with water to remove ABA from the surface. Five to 10 seedlings (~100 mg) were pooled to form 1 replicate, and ABA levels were measured (mean ± SE; N = 5). Asterisks indicate significant differences between the respective ABA-treated and non-treated groups determined by Student’s <i>t</i>-test (***, P < 0.001).</p

Sequence alignment of <i>C</i>. <i>australis</i> and <i>A</i>. <i>thaliana</i> ABA receptors.

<p>Secondary structural elements are indicated above the primary sequences. Helices and strands are shown as blue cylinders and arrows, respectively. The 4 conserved loops CL1–CL4 are highlighted by the magenta lines. The 4 ABA receptors of <i>C</i>. <i>australis</i> are CaPYL1 to CaPYL4, and the 14 ABA receptors of <i>A</i>. <i>thaliana</i> are AtPYR1 and AtPYL1 to AtPYL13. The alignment was done using ClustalX2.1.</p

<i>C</i>. <i>australis</i> seedlings show highly decreased sensitivity to ABA during seed germination.

<p>Tomato and <i>C</i>. <i>australis</i> seeds were sterilized and sown on 1/2 MS medium in the presence of different concentrations of ABA and incubated in a growth chamber (24°C, 16 h light/8 h dark cycle). The germination rates (mean ± SE; N = 30) of tomato (<b>A</b>) and <i>C</i>. <i>australis</i> (<b>B</b>) seeds were recorded daily. The experiment was repeated twice with very similar results.</p