About this Research Topic
Since its discovery more than a century ago and the conferral of several Nobel laureates for ground-breaking works concerning the molecule, nicotinamide adenine dinucleotide (NAD) is recognized as a fascinating cornerstone of cellular metabolism for all living organisms. This ubiquitous pyridine nucleotide (and its phosphorylated relative, NADP) is an energy cofactor and signal-carrying molecule exerting vital functions in metabolic pathways and regulatory processes. A multitude of enzymatic reactions rely on the electron-transferring properties of NAD(P) (and their reduced forms NAD(P)H), particularly dehydrogenases, which are important for energy metabolism. Consequently, a balanced NAD metabolism and homeostasis hold a key position in maintaining normal plant growth and development.
Research on the roles of NAD in plants has been predominantly carried out in the model species Arabidopsis thaliana using both molecular and genomic tools. These molecular studies involved transcript, protein and metabolite profiling, and revealed a particularly complex signaling network that can impact not only the core biochemistry of the plant (e.g. photosynthesis, respiration, energy), but also responses to various stress, more importantly immune responses. Remarkably, emerging evidence further indicates that NAD can be released into the extracellular space, where it is processed or sensed by cell receptors. Recently, a lectin receptor kinase has been reported to function as extracellular NAD+-binding receptor in Arabidopsis thaliana, thus demonstrating that extracellular NAD+ acts as an endogenous signaling molecule in plants. Hence, plant cells are able to perceive NAD as signals and subsequently activate signaling transduction. However, the detailed mechanisms by which NAD acts as a regulator of plant physiology and responses to the environment are still poorly understood. In addition, knowledge is largely lacking about sensing mechanism of intracellular NAD status, subcellular and intercellular trafficking mechanism of NAD, and the regulatory mechanism of NAD-processing components, where input is necessary from diverse major crops. Interestingly, metabolic modelling, as an emerging tool, promises to deliver insightful outputs to allow for detection of NAD fluxes across a range of physiological contexts. Here, we would like to gather the comprehensive knowledge accrued to date on the functions of NAD in plants, and how it can be applied in order to improve future plant production and protection.
This Research Topic aims to expand our understanding of the roles of NAD in modulating plant functions, with a special focus on metabolic regulations during plant development and signaling responses to environmental constraints. We encourage all types of submissions of Original Research, Review and Method papers, which would provide new insights into the many aspects of NAD metabolism and signaling, and benefit the scientific community working on NAD biology.
Keywords: NAD, NAD Signaling, NAD Metabolism
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