Abstract
Nitrate (NO3–) and auxin are key regulators of root growth and development, modulating the signalling cascades in auxin-induced lateral root formation. Auxin biosynthesis, transport, and transduction are significantly altered by nitrate. A decrease in nitrate (NO3–) supply tends to promote auxin translocation from shoots to roots and vice-versa. This nitrate mediated auxin biosynthesis regulating lateral roots growth is induced by the nitrate transporters and its downstream transcription factors. Most nitrate responsive genes (short-term and long-term) are involved in signalling overlap between nitrate and auxin, thereby inducing lateral roots initiation, emergence, and development. Moreover, in the auxin signalling pathway, the varying nitrate supply regulates lateral roots development by modulating the auxin accumulation in the roots. Here, we focus on the roles of nitrate responsive genes in mediating auxin biosynthesis in Arabidopsis root, and the mechanism involved in the transport of auxin at different nitrate levels. In addition, this review also provides an insight into the significance of nitrate responsive regulatory module and their downstream transcription factors in root system architecture in the model plant Arabidopsis thaliana.
Highlights
Roots are crucial for the anchorage of plants in the soil and facilitate the translocation of water and mineral nutrients
Several nitrate responsive genes involved in nitrate signalling promotes lateral root growth
These genes are characterized in terms of nitrate regulatory genes, which build up signalling overlap between nitrate and auxin, and subsequently induce lateral roots (LRs) initiation, emergence, and development [50]
Summary
Roots are crucial for the anchorage of plants in the soil and facilitate the translocation of water and mineral nutrients. IAA is the most researched and best naturally occurring active auxin [12], and it plays a specific role in the control of systemic inhibition of fresh lateral roots (LRs) developments in response to the sufficient supply of nitrate [16]. Both external NO3− and IAA supply significantly influence the auxin concentration in the tiller nodes [17]. We focus on an in-depth role of NO3− in auxin-induced signalling, and the relationship between NO3− and IAA transcript levels in the regulation of lateral root initiation, emergence, and development in the model plant Arabidopsis thaliana
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