Published by Oxford University Press [2006] on behalf of the Society for Experimental Biology.
FOCUS PAPER |
Preface to Nitric Oxide Signalling: Plant Growth and Development
Interest in nitric oxide (NO) as an endogenous and potent regulator of plant growth and development has grown exponentially in the last few years. The Focus Section in this issue of Journal of Experimental Botany (JXB) contains six papers based on invited talks from a session held at the Society for Experimental Biology (SEB) Annual Meeting in Barcelona, Spain, in July 2005. This session, addressing Nitric Oxide Signalling: Plant Growth and Development, brought together most of the leading plant NO researchers in Europe as well as participants from the USA and Brazil, in what was probably the first-ever meeting devoted to NO and plant biology (Abstracts available at http://www.sebiology.org/).
Nigel Crawford discusses various aspects of NO biosynthesis and signalling, particularly in relation to AtNOS1, the first (and so far only) plant nitric oxide synthase to be identified. The availability of a mutant impaired in AtNOS1 activity has facilitated various genetic analyses of NO signalling. Massimo Delledonne and his colleagues discuss mechanisms by which NO is removed, concentrating on the action of non-symbiotic haemoglobins. It now seems clear that a key, and hitherto unknown, function of such haemoglobins is reaction with, and thereby removal of, NO. NO is synthesized and functions in many if not all tissues, but in their article Christine Stöhr and Stefanie Stremlau focus on roots, a system sometimes overlooked. Roots are often exposed to high concentrations of nitrate in the soil, which may impact on root NO content, as nitrite, derived from nitrate via nitrate reductase (NR), can serve as a substrate for NO generation, either non-enzymatically, via NR itself or via an as-yet-uncharacterized enzyme (nitrite:NO reductase) that has been described by Stöhr and Stremlau. The importance of NO to plant biology was first highlighted when it was shown to be a key plant defence signal, being generated in response to pathogen challenge and participating in the programmed cell death and altered gene expression that are characteristic of challenged cells. Luis Mur and his colleagues discuss the potential biological roles of NO during plant–pathogen interactions and some of the mechanisms by which NO might exert its function.They also address aspects of NO biology in a fungal pathogen. NO is a universal signal, so understanding what it does and how it is interpreted by both partners in such interactions is likely to be significant. Jorg Dürner and his colleagues take as their theme the regulation of gene expression by NO. They survey the range of genes whose expression is NO-sensitive and discuss the potential molecular mechanisms by which gene expression could be modulated. Interestingly, they point to the lack of coincidence between the patterns of NO-regulated gene expression reported by different researchers, emphasizing the importance of experimental conditions. Finally, Paul Bethke and his colleagues review the role of NO as an agent that can break seed dormancy. Certain N-containing compounds have long been known to break dormancy and Bethke et al. describe the role of NO in this process. Importantly, they also show that cyanide, released with NO from the NO donor sodium nitroprusside, is similarly effective—important because this demonstrates the need for caution when using NO donors.
In summary, these six papers convey the advances, excitement and controversies associated with NO and plant biology. They cover a wide range of topics and provide many ideas for future research developments.
We thank the SEB, the Cell Signalling and Plant Development Groups, JXB, and EMBO for their financial support of this session in Barcelona. We also thank the authors, the reviewers, and the JXB team for their expertise and support during the production of this Focus Section.
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