<p>To determine whether the relative expression levels of the drought stress-responsive MAPKKK genes differed among varieties induced by drought, ZD619 and the 6 inbred maize lines J24, J853, X178, E28, C8605-2, 200B, Q319 and B73 were used. Lines X178, J24 are drought-resistant lines; 200B and E28 have poor drought tolerance. The eight MAPKKK genes are <i>GRMZM2G305066</i> (<i>ZmMAPKKK18</i>), <i>GRMZM2G165099</i> (<i>ZmMAPKKK19</i>), <i>GRMZM2G476477</i> (<i>ZmMAPKKK20</i>), <i>GRMZM2G173965</i> (<i>ZmMAPKKK21</i>), <i>GRMZM2G041774</i> (<i>ZmMAPKKK22</i>), <i>GRMZM2G021416</i> (<i>ZmMAPKKK26</i>), <i>GRMZM2G063069</i> (<i>ZmMAPKKK56</i>), <i>GRMZM2G474546</i> (<i>ZmMAPKKK73</i>). * indicates significant differences in comparison with the control at P < 0.05 respectively. Error bars indicate standard deviation for three replicates.</p
