Li Ning, Sun Lirong, Zhang Liyue, Song Yalin, Hu Panpan, Li Cui, Hao Fu Shun
State Key Laboratory of Cotton Biology, Henan Key Laboratory of Plant Stress Biology, College of Life Sciences, Henan University, Jinming Street, Kaifeng, 475004, Henan, China.
Planta. 2015 Mar;241(3):591-602. doi: 10.1007/s00425-014-2204-1. Epub 2014 Nov 16.
NADPH oxidase AtrbohD an d AtrbohF negatively modulate lateral root development by changing the peroxidase activity and increasing the local generation of superoxide in primary roots of Arabidopsis in an auxin-independent manner. NADPH oxidase subunits AtrbohD and AtrbohF play pivotal roles in regulating growth, development and stress responses in Arabidopsis. However, whether they modulate lateral root (LR) formation has not yet been addressed, and the detailed mechanisms underlying the process remain unanswered. Here, we show that two null double mutants atrbohD1/F1 and atrbohD2/F2, in which both AtrbohD and AtrbohF genes are disrupted, had remarkably higher LR density than wild-type (WT), or the single mutant atrbohD1 and atrbohF1. Compared to WT, the double mutants exhibited early emerged LRs and enhanced density of lateral root primordia (LRP). Unexpectedly, the production of superoxide (O2 (-)), but not hydrogen peroxide, in the mature area of the primary root containing LRs significantly increased in the double mutants relative to that in WT. Further experiments revealed that the local accumulation of O2 (-) led to the enhancement of LR density in the double mutants. Moreover, the deficiency of AtrbohD and AtrbohF caused a marked increase in peroxidase activity in the mature root zone, which contributed to the localized accumulation of O2 (-) and the elevated LR density in the double mutants. Furthermore, the double mutants were not sensitive to exogenous auxin naphthalene acetic acid or auxin transport inhibitor 1-N-naphthylphthalamic acid in terms of LR formation. The auxin response of LRP in vivo in atrbohD1/F1 was also similar to that in WT. Taken together, these results suggest that AtrbohD and AtrbohF negatively modulate LR development by controlling the local generation of superoxide in an auxin-independent manner. These findings provide new insights into the mechanisms of NADPH oxidase-mediated regulation of LR branching in Arabidopsis.
NADPH氧化酶AtrbohD和AtrbohF通过改变过氧化物酶活性并以生长素非依赖的方式增加拟南芥初生根中超氧化物的局部产生，从而对侧根发育产生负调控作用。NADPH氧化酶亚基AtrbohD和AtrbohF在调节拟南芥的生长、发育和应激反应中起关键作用。然而，它们是否调节侧根（LR）形成尚未得到解决，该过程的详细机制仍未明确。在此，我们表明，AtrbohD和AtrbohF基因均被破坏的两个无效双突变体atrbohD1/F1和atrbohD2/F2的LR密度显著高于野生型（WT）或单突变体atrbohD1和atrbohF1。与WT相比，双突变体表现出侧根早期出现且侧根原基（LRP）密度增加。出乎意料的是，相对于WT，双突变体中含有LR的初生根成熟区域中超氧化物（O2（-））而非过氧化氢的产生显著增加。进一步的实验表明，O2（-）的局部积累导致双突变体中LR密度增加。此外，AtrbohD和AtrbohF的缺陷导致成熟根区过氧化物酶活性显著增加，这有助于双突变体中O2（-）的局部积累和LR密度升高。此外，在LR形成方面，双突变体对外源生长素萘乙酸或生长素运输抑制剂1-N-萘基邻苯二甲酸不敏感。atrbohD1/F1中LRP的体内生长素反应也与WT相似。综上所述，这些结果表明，AtrbohD和AtrbohF通过以生长素非依赖的方式控制超氧化物的局部产生来对LR发育产生负调控作用。这些发现为NADPH氧化酶介导的拟南芥LR分支调控机制提供了新的见解。
