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Published on: April 17, 2016
Auxin Biosynthesis, Transport, Signaling, and Its Roles in Plant Leaf Morphogenesis
Han Zheng1, Qian Zhang2, Qun Liu2
1Shandong Key Laboratory of Bulk Open-Field Vegetable Breeding, Ministry of Agriculture and Rural Affairs Key Laboratory of Huang Huai Protected Horticulture Engineering, Institute of Vegetables, Shandong Academy of Agricultural Sciences, Jinan 250100, China.
Abstract:
Leaf morphogenesis is governed by a tightly integrated regulatory network centered on auxin, which operates through a sequential axis of synthesis, transport, and signal transduction. This review elucidates how pivotal molecular hubs previously identified in this regulatory network, including biosynthetic enzymes, polar transporters, and auxin response factors, interconnect through dynamic feedback mechanisms to orchestrate leaf initiation, polarity establishment, and the determination of its final size and shape. Notably, recent breakthroughs are transforming the field: the re-evaluation of established pathways like indole-3-acetaldoxime (IAOx), whose direct contribution to auxin pools is under scrutiny, hinting at the existence of undiscovered enzymes or alternative metabolic branches and the paradigm-shifting discovery that cAMP functions as a second messenger produced by Transport Inhibitor Resistant 1/Auxin signaling F-box (TIR1/AFB) receptors, which directly activates Auxin Response Factor (ARF)-mediated transcription. These foundational mechanistic insights provide the critical groundwork for application. Key network nodes-such as PIN-FORMED (PIN) transporters and YUCCA (YUC) flavin-containing monooxygenases-are now validated targets for crop improvement. Consequently, the elucidated network serves as a blueprint for rationally designing crop architecture.
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