生物谷报道：据最新出版的Journal of Integrative Plant Biology (《植物学报》)杂志2007年第七期报道，一直被认为是有毒气体之一的一氧化碳（CO），可以通过一氧化氮（NO）信号来介导，从而诱导油菜的侧根形成。
众所周知，根系是植物体的一个重要组成部分，植物体正常生命活动所需要的水分和矿质营养物都是由根系从土壤中吸收而来，同时根系对植物体具有机械支撑作用。因此根系发育的好坏直接影响着植物体的生长状况，因而与农业生产息息相关。众所周知，在种子萌发后只能形成一条主根，其后产生的不定根的数目也是有限的，因此侧根的发生对于形成庞大的根系不可缺少的。良好的根系建成是植物健壮生长和抗逆高产的基础。侧根是植物根系的重要组成部分，对养分吸收、锚定植株以及根际共生系统的建立起关键作用。侧根的发生发育除了受遗传因素控制外，还受环境因素的影响，尤其受生长介质中各种养分有效性的影响。研究侧根发生对于提高农作物产量、丰产丰收有着巨大的实践与理论指导意义，正因如此，在过去的几十年里，人们对侧根的发生进行了大量的研究，迄今这一研究领域仍是国际上的一个研究热点。
一直以来，CO仅仅被认为是一种有毒有害的气体，例如使用化石燃料导致的大气污染、引起温室效应及人体煤气中毒等等。近年来，一系列动物领域内的研究发现在神经传导和血管收缩方面，低浓度CO具有与NO类似的功能。其实，早在上个世纪50~60年代，在多种植物的发育过程中就观察到低浓度CO释放的现象，表明植物体释放CO可能是一个普遍存在的现象。但由于当时条件所限，一直无法进行深入的研究，其生物学功能也一直不为人们所知。从上世纪90年代以来，尤其在最近，才逐步有报道发现CO可以参与调控：植物种子的破休眠与诱导萌发、不定根的发生以及各种逆境下农作物的抗逆性，而类似的功能NO都曾有报道。
2006年，世界知名的《实验植物学杂志》（Journal of Experimental Botany）报道发现NO可以诱导番茄侧根发生，这也佐证了我国的Journal of Integrative Plant Biology (《植物学报》)今年的这一报道。同时，这一结果也为揭示植物侧根发生的意义和机理提供了更详细的证据，因此在解开植物侧根发生调节规律之谜的道路上又向前迈出了一步。
报道中指出：低浓度CO供体及气体都可以明显地诱导油菜侧根发生，并且这一过程具有明显的CO特异性。当CO被清除后，CO的诱导效应即被明显削弱。该报道还发现，CO诱导侧根发生的效应是通过NO信号实现的：将NO清除后，CO的诱导作用也明显减弱。此外，用一种与NO特异性结合的荧光探针标记NO，观察发现CO可以增强NO荧光，而这些NO恰恰分布于正在发生的侧根原基上；同样，将CO清除后，这一现象也无法观察到。这篇文章的模型是：CO可以诱导侧根发生，并且其诱导作用则是通过NO来实现。
目前，该研究小组关于侧根发生的研究还在继续，探讨的问题包括：CO与NO之间是如何实现对话的？在侧根发生过程中CO或NO是否作为一个基本事件普遍存在？对这些问题的回答将引导人们提出更加深刻的疑问，直至最终揭示植物侧根发生调节的所有秘密。
该研究小组还发现，在其他一些方面，CO也具有明显的功效，如可以显著提高农作物各种逆境耐性，包括干旱、涝害、盐渍和重金属胁迫等。各种CO作用机制的剖析，不仅在揭示植物生长发育和胁迫耐性奥秘方面具有重要的科研价值，而且可以在运用CO优化农业生产的过程中发挥指导作用。总之，人们将在对CO随心所欲的应用过程中，引领现代农业生产进入到另一个新时代。（援引人民网）
原始出处:
Journal of Integrative Plant Biology
Volume 49 Issue 7 Page 1070-1079, July 2007
To cite this article: Ze-Yu Cao, Wei Xuan, Zhao-Yang Liu, Xin-Na Li, Nan Zhao, Peng Xu, Zhe Wang, Rong-Zhan Guan, Wen-Biao Shen (2007)
Carbon Monoxide Promotes Lateral Root Formation in Rapeseed
Journal of Integrative Plant Biology 49 (7), 1070–1079.
doi:10.1111/j.1672-9072.2007.00482.x
Carbon Monoxide Promotes Lateral Root Formation in Rapeseed
Supported by the Grant to Innovative Young Scholars of Jiangsu Province in China (BK2004417), the Program for Changjiang Scholars and Innovative Research Team in China (PCSIRT), and by the Student Research Training (SRT) Project of Nanjing Agricultural University (0506B07, KFJJ200501 and JD200502).
*These authors contributed equally to this work. **Authors for correspondence.
Tel (Fax): +86 (0)25 8439 6542;
E-mail: <wbshenh@njau.edu.cn and guanrzh@njau.edu.cn>.
Carbon monoxide (CO), an odorless, tasteless and colorless gas, has recently proved to be an important bioactive or signal molecule in mammalian cells, with its effects mediated mainly by nitric oxide (NO). In the present report, we show that exogenous CO induces lateral root (LR) formation, an NO-dependent process. Administration of the CO donor hematin to rapeseed (Brassica napus L. Yangyou 6) seedlings for 3 days, dose-dependently promoted the total length and number of LRs. These responses were also seen following the application of gaseous CO aqueous solutions of different saturated concentrations. Furthermore, the actions of CO on seedlings were fully reversed when the CO scavenger hemoglobin (Hb) or the CO-specific synthetic inhibitor zinc protoporphyrin-IX (ZnPPIX) were added. Interestingly, depletion of endogenous NO using its specific scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO) or the nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (l-NAME), led to the complete abolition of LR development, illustrating an important role for endogenous NO in the action of CO on LR formation. However, the induction of LR development by 200 μmol/L sodium nitroprusside (SNP), an NO donor, was not affected by the presence or absence of ZnPPIX. Furthermore, using an anatomical approach combined with laser scanning confocal microscopy with the NO-specific fluorophore 4,5-diaminofluorescein diacetate, we observed that both hematin and SNP increased NO release compared with control samples and that the NO signal was mainly distributed in the LR primordia (LRP), especially after 36 h treatment. The LRP were found to have similar morphology in control, SNP- and hematin-treated seedlings. Similarly, the enhancement of the NO signal by CO at 36 h was differentially quenched by the addition of cPTIO, l-NAME, ZnPPIX and Hb. In contrast, the induction of NO caused by SNP was not affected by the application of ZnPPIX. Therefore, we further deduced that CO induces LR formation probably mediated by the NO/NOS pathway and NO may act downstream of CO signaling, which has also been shown to occur in animals.
