Kang Na Young, Lee Han Woo, Kim Jungmook
Department of Bioenergy Science and Technology and Kumho Life Science Laboratory, Chonnam National University, Gwangju 500-757, Korea.
Plant Cell Physiol. 2013 Aug;54(8):1326-34. doi: 10.1093/pcp/pct081. Epub 2013 Jun 6.
The developmental process of lateral root formation consists of priming, initiation, primordium development and the emergence of lateral roots from the primary root. Molecular genetic studies with Arabidopsis have revealed several key transcriptional regulators involved in lateral root development. However, their functional interaction has not been fully characterized yet. Here we utilized a genetic approach to understand some of these interactions, revealing that PUCHI functioning in morphogenesis of early lateral root primordium is regulated downstream of ARF7/ARF19 and acts with LBD16(ASL18)/LBD18(ASL20) to regulate lateral root development. We showed that auxin-responsive expression of PUCHI was significantly reduced in arf7 or arf19 single mutants and completely abolished in arf7 arf19 double mutants. Consistent with this, β-glucuronidase (GUS) expression under the PUCHI promoter in arf7 arf19 was greatly reduced in the lateral root primordium compared with that in the wild type and did not respond to exogenous auxin. Results of GUS expression analyses under the PUCHI, LBD16 or LBD18 promoter in lbd16, lbd18 single and double mutants or puchi demonstrated that PUCHI and LBD16 or LBD18 do not regulate each other's expression. Lateral root phenotypes of double and triple mutants of lbd16, lbd18 and puchi showed that the puchi mutation in lbd16 and lbd18 mutants synergistically decreased the number of emerged lateral roots. These analyses also showed that puchi affected lateral root primordium development of lbd16 or lbd18 additively but differentially. Taken together, these results suggest that PUCHI co-acts with LBD16 and LBD18 to control lateral root primordium development and lateral root emergence.
侧根形成的发育过程包括起始、启动、原基发育以及侧根从主根中长出。对拟南芥的分子遗传学研究揭示了几个参与侧根发育的关键转录调节因子。然而，它们的功能相互作用尚未得到充分表征。在这里，我们利用遗传学方法来了解其中的一些相互作用，结果表明，在早期侧根原基形态发生中起作用的PUCHI受ARF7/ARF19下游调控，并与LBD16(ASL18)/LBD18(ASL20)共同作用来调节侧根发育。我们发现，在arf7或arf19单突变体中，PUCHI的生长素响应性表达显著降低，而在arf7 arf19双突变体中则完全消失。与此一致的是，与野生型相比，arf7 arf19中PUCHI启动子驱动的β-葡萄糖醛酸酶（GUS）在侧根原基中的表达大大降低，并且对外源生长素没有反应。在lbd16、lbd18单突变体和双突变体或puchi中，对PUCHI、LBD16或LBD18启动子驱动的GUS表达分析结果表明，PUCHI与LBD16或LBD18并不相互调节彼此的表达。lbd16、lbd18和puchi双突变体和三突变体的侧根表型表明，lbd16和lbd18突变体中的puchi突变协同减少了长出的侧根数量。这些分析还表明，puchi对lbd16或lbd18的侧根原基发育有累加但有差异的影响。综上所述，这些结果表明，PUCHI与LBD16和LBD18共同作用来控制侧根原基发育和侧根长出。
