Singh Neha, Bhatla Sathish C
a Laboratory of Plant Physiology and Biochemistry, Department of Botany , University of Delhi , Delhi - India.
Plant Signal Behav. 2018;13(5):e1473683. doi: 10.1080/15592324.2018.1473683. Epub 2018 Jun 25.
Nitric oxide (NO) is established as a modulator of various developmental processes in plants through its interaction with multiple enzymatic and non-enzymatic biomolecules. Lateral root (LR) induction and extension in sunflower (Helianthus annuus L.) has been observed to be governed by a probable crosstalk between NO and ethylene biosynthesizing enzyme-ACC oxidase. NaCl (120 mM) stress not only lowers LR induction but also reduces their extension growth. Quenching of endogenous NO by raising seedlings in presence of 40 µM hemoglobin in the growth medium does not affect LR induction but lowers their extension growth. NaCl stress and NO depletion have additive effects on the enhancement of ACC oxidase activity, leading to enhanced ethylene biosynthesis. Role of NO has been further confirmed by raising sunflower seedlings in the presence of 20-60 µM of two NO donors, sodium nitroprusside (SNP) and diethylenetriamine NONOate (DETA). LR extension growth was higher with DETA than SNP as NO donor at 40 µM. Iron-deficiency also promoted LR proliferation. It also significantly lowered ACC oxidase activity in the seedling roots in response to salt stress. Based on the present findings it is proposed that salt stress-mediated LR proliferation is regulated by NO through its binding with ACC oxidase (an iron-containing enzyme). This results in the formation of a stable ternary complex (ACC-ACC oxidase-NO) which leads to the reduction in ethylene biosynthesis. Lesser availability of ethylene consequently brings about enhanced LR formation.
一氧化氮（NO）通过与多种酶和非酶生物分子相互作用，已被确认为植物各种发育过程的调节剂。已观察到向日葵（Helianthus annuus L.）侧根（LR）的诱导和延伸受NO与乙烯生物合成酶——ACC氧化酶之间可能的相互作用调控。120 mM的NaCl胁迫不仅降低了LR的诱导，还减少了它们的延伸生长。在生长培养基中添加40 μM血红蛋白来淬灭内源性NO，不会影响LR的诱导，但会降低它们的延伸生长。NaCl胁迫和NO消耗对ACC氧化酶活性的增强具有累加效应，导致乙烯生物合成增加。在20 - 60 μM的两种NO供体硝普钠（SNP）和二乙三胺 NONO 酸盐（DETA）存在的情况下培养向日葵幼苗，进一步证实了NO的作用。在40 μM时，作为NO供体，DETA处理的LR延伸生长高于SNP处理。缺铁也促进了LR的增殖。它还显著降低了盐胁迫下幼苗根系中ACC氧化酶的活性。基于目前的研究结果，推测盐胁迫介导的LR增殖是由NO通过与ACC氧化酶（一种含铁酶）结合来调节的。这导致形成稳定的三元复合物（ACC - ACC氧化酶 - NO），从而减少乙烯生物合成。因此，乙烯可用性降低进而导致LR形成增加。
