1.
The role of auxin in nitrogen-modulated shoot branching.
Hou, M, Wu, D, Li, Y, Tao, W, Chao, L, Zhang, Y
Plant signaling & behavior. 2021;(4):1885888
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Abstract
Shoot branching is determined by axillary bud formation and outgrowth and remains one of the most variable determinants of yield in many crops. Plant nitrogen (N) acquired mainly in the forms of nitrate and ammonium from soil, dominates plant development, and high-yield crop production relies heavily on N fertilization. In this review, the regulation of axillary bud outgrowth by N availability and forms is summarized in plant species. The mechanisms of auxin function in this process have been well characterized and reviewed, while recent literature has highlighted that auxin export from a bud plays a critical role in N-modulating this process.
2.
PIN-driven auxin transport emerged early in streptophyte evolution.
Skokan, R, Medvecká, E, Viaene, T, Vosolsobě, S, Zwiewka, M, Müller, K, Skůpa, P, Karady, M, Zhang, Y, Janacek, DP, et al
Nature plants. 2019;(11):1114-1119
Abstract
PIN-FORMED (PIN) transporters mediate directional, intercellular movement of the phytohormone auxin in land plants. To elucidate the evolutionary origins of this developmentally crucial mechanism, we analysed the single PIN homologue of a simple green alga Klebsormidium flaccidum. KfPIN functions as a plasma membrane-localized auxin exporter in land plants and heterologous models. While its role in algae remains unclear, PIN-driven auxin export is probably an ancient and conserved trait within streptophytes.
3.
Selective auxin agonists induce specific AUX/IAA protein degradation to modulate plant development.
Vain, T, Raggi, S, Ferro, N, Barange, DK, Kieffer, M, Ma, Q, Doyle, SM, Thelander, M, Pařízková, B, Novák, O, et al
Proceedings of the National Academy of Sciences of the United States of America. 2019;(13):6463-6472
Abstract
Auxin phytohormones control most aspects of plant development through a complex and interconnected signaling network. In the presence of auxin, AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) transcriptional repressors are targeted for degradation by the SKP1-CULLIN1-F-BOX (SCF) ubiquitin-protein ligases containing TRANSPORT INHIBITOR RESISTANT 1/AUXIN SIGNALING F-BOX (TIR1/AFB). CULLIN1-neddylation is required for SCFTIR1/AFB functionality, as exemplified by mutants deficient in the NEDD8-activating enzyme subunit AUXIN-RESISTANT 1 (AXR1). Here, we report a chemical biology screen that identifies small molecules requiring AXR1 to modulate plant development. We selected four molecules of interest, RubNeddin 1 to 4 (RN1 to -4), among which RN3 and RN4 trigger selective auxin responses at transcriptional, biochemical, and morphological levels. This selective activity is explained by their ability to consistently promote the interaction between TIR1 and a specific subset of AUX/IAA proteins, stimulating the degradation of particular AUX/IAA combinations. Finally, we performed a genetic screen using RN4, the RN with the greatest potential for dissecting auxin perception, which revealed that the chromatin remodeling ATPase BRAHMA is implicated in auxin-mediated apical hook development. These results demonstrate the power of selective auxin agonists to dissect auxin perception for plant developmental functions, as well as offering opportunities to discover new molecular players involved in auxin responses.
4.
Auxin distribution is differentially affected by nitrate in roots of two rice cultivars differing in responsiveness to nitrogen.
Song, W, Sun, H, Li, J, Gong, X, Huang, S, Zhu, X, Zhang, Y, Xu, G
Annals of botany. 2013;(7):1383-93
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Abstract
BACKGROUND AND AIMS Although ammonium (NH4(+)) is the preferred form of nitrogen over nitrate (NO3(-)) for rice (Oryza sativa), lateral root (LR) growth in roots is enhanced by partial NO3(-) nutrition (PNN). The roles of auxin distribution and polar transport in LR formation in response to localized NO3(-) availability are not known. METHODS Time-course studies in a split-root experimental system were used to investigate LR development patterns, auxin distribution, polar auxin transport and expression of auxin transporter genes in LR zones in response to localized PNN in 'Nanguang' and 'Elio' rice cultivars, which show high and low responsiveness to NO3(-), respectively. Patterns of auxin distribution and the effects of polar auxin transport inhibitors were also examined in DR5::GUS transgenic plants. KEY RESULTS Initiation of LRs was enhanced by PNN after 7 d cultivation in 'Nanguang' but not in 'Elio'. Auxin concentration in the roots of 'Nanguang' increased by approx. 24 % after 5 d cultivation with PNN compared with NH4(+) as the sole nitrogen source, but no difference was observed in 'Elio'. More auxin flux into the LR zone in 'Nanguang' roots was observed in response to NO3(-) compared with NH4(+) treatment. A greater number of auxin influx and efflux transporter genes showed increased expression in the LR zone in response to PNN in 'Nanguang' than in 'Elio'. CONCLUSIONS The results indicate that higher NO3(-) responsiveness is associated with greater auxin accumulation in the LR zone and is strongly related to a higher rate of LR initiation in the cultivar 'Nanguang'.