Key Laboratory of Arid and Grassland Agroecology (Ministry of Education), School of Life Sciences, Lanzhou University, Lanzhou Gansu 730000, People's Republic of China.
J Plant Physiol. 2011 Oct 15;168(15):1771-9. doi: 10.1016/j.jplph.2011.04.009.
Phytochrome interacting factors (PIFs) are members of a subfamily of basic helix-loop-helix transcript factors and have been proposed to act as positive regulators of hypocotyl elongation under normal condition. Here, we show that PIF1, 3, 4, 5 together play a central role in sucrose-induced hypocotyl elongation. When seedlings grown in light were transferred to darkness, exogenously applied sucrose significantly induced hypocotyl elongation in wild type Col-0, but this effect was impaired in all tested pif mutants, especially in the quadruple mutant pif1pif3pif4pif5 (pifq). Subsequent experiments showed that under various light/dark (L/D) cycle conditions sucrose still markedly induced hypocotyl elongation in Col-0, but exhibited little effects in pifq. Phytohormone gibberellins (GAs) have been proven to be required for sucrose-induced hypocotyl elongation, but application of GA(3) (an active form of GAs) was not able to rescue the impairment observed in pifq, suggesting that impairment of sucrose-induced hypocotyl elongation in pifq is not due to the reduced endogenous GAs. Interestingly, through RT-PCR assay, we found that sucrose up-regulated the transcript level of PIF1, 3, 4, 5 in darkness. Furthermore, this effect was dependent on the presence of GAs. Additionally, under continuous light condition, sucrose markedly inhibited the hypocotyl elongation in Col-0 but not in pifq, whereas exogenous GA(3) could recover the repression in Col-0 but only showed slight effect in pifq. These results collectively indicate that PIFs together with GAs control the effect of sucrose on hypocotyl elongation in Arabidopsis seedlings.
光敏色素相互作用因子（PIFs）是基本螺旋-环-螺旋转录因子亚家族的成员，被认为在正常条件下作为下胚轴伸长的正调节剂起作用。在这里，我们表明 PIF1、3、4、5 共同在蔗糖诱导的下胚轴伸长中起核心作用。当在光照下生长的幼苗被转移到黑暗中时，外源施加的蔗糖显著诱导野生型 Col-0 中的下胚轴伸长，但在所有测试的 pif 突变体中，这种效应都受到损害，特别是在四重突变体 pif1pif3pif4pif5（pifq）中。随后的实验表明，在各种光/暗（L/D）循环条件下，蔗糖仍能显著诱导 Col-0 中的下胚轴伸长，但在 pifq 中几乎没有作用。植物激素赤霉素（GAs）已被证明是蔗糖诱导的下胚轴伸长所必需的，但 GA（3）（GA 的一种活性形式）的应用不能挽救 pifq 中观察到的损伤，表明 pifq 中蔗糖诱导的下胚轴伸长损伤不是由于内源性 GAs 的减少。有趣的是，通过 RT-PCR 分析，我们发现蔗糖在黑暗中上调了 PIF1、3、4、5 的转录水平。此外，这种效应依赖于 GAs 的存在。此外，在连续光照条件下，蔗糖显著抑制 Col-0 中的下胚轴伸长，但在 pifq 中则没有，而外源 GA（3）可以恢复 Col-0 中的抑制作用，但在 pifq 中仅显示轻微作用。这些结果共同表明，PIFs 与 GAs 一起控制蔗糖对拟南芥幼苗下胚轴伸长的影响。
