![]() The tt4 root phenotype was reversed by genetic and chemical complementation. We observed the tt4 and fls1 mutants, which produce no flavonols, have increased lateral root emergence. We examined potential roles for flavonols in this process using Arabidopsis thaliana mutants with defects in genes encoding key enzymes in flavonoid biosynthesis. ![]() Flavonoids modulate plant development, but whether and how they impact lateral root development is unclear. The potential ways how PAO5 may influence direct shoot organogenesis from Arabidopsis LRPs are discussed.įlavonoids are a class of specialized metabolites with subclasses including flavonols and anthocyanins, which have unique properties as antioxidants. This was correlated with Spd accumulation in the roots and ROS accumulation in the converting LRPs. The expression of Arabidopsis POLYAMINE OXIDASE 5 (AtPAO5) was shown to be specifically high during the process and its ectopic overexpression increased the LRP-to-shoot conversion efficiency. However, the effect of PAs on shoot meristem formation might also be dependent on their catabolism. The high endogenous Spd level could be due to enhanced synthesis as indicated by the augmented relative expression of PA synthesis genes (AtADC1,2, AtSAMDC2,4, AtSPDS1,2) during the process. We report that the level of PAs, especially that of spermidine (Spd), increased during meristem conversion and the application of exogenous Spd improved its efficiency. In this system, no callus formation takes place. Interestingly, the lateral root primordia (LRPs) of Arabidopsis can be directly converted to shoot meristems by exogenous cytokinin application. Besides plant hormones, the role of polyamines (PAs) has been implicated in these processes. Most of these regeneration pathways are indirect and involve callus formation. Plants can be regenerated from various explants/tissues via de novo shoot meristem formation. Collectively, this study improves our understanding of the highly sophisticated processes involved in exocytic vesicular trafficking-mediated polar auxin transport and lateral root initiation in plants. Finally, the b1l-1/exo70b1-1 double-mutant exhibited a significant increase in the number of lateral roots compared to the wildtype, b1l-1, and exo70b1-1. Moreover, B1L interacts with the exocyst and functions in recycling PIN2-GFP. Consistently, b1l mutants exhibited higher levels of auxin efflux carriers PIN1-GFP and PIN3-GFP in lateral root primordia. Additionally, auxin transport-inhibitory treatment indicated that B1L regulates auxin efflux. Exogenous auxin treatment confirmed that the lateral root phenotype correlated closely with auxin levels. Furthermore, DR5::GUS expression analyses revealed that auxin levels were higher in lateral root primordia of the b1l mutant than in the wild-type. B1L is highly expressed in Arabidopsis roots, and genetic and cellular analyses have revealed that B1L is mainly involved in lateral root primordia initiation. Here, we demonstrate an essential regulatory mechanism of B1L that interacts with the exocyst to regulate PIN-mediated polar auxin transport and lateral root initiation. ![]() Although exocytic vesicle trafficking plays an important role in PIN-auxin-efflux carrier recycling, and polar auxin transport during lateral root formation, however, the mechanistic details of these processes are not well understood. Auxin and auxin-mediated signaling pathways involved in the regulation of lateral root development are well documented. ![]()
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