The auxin receptor TIR1 homolog (PagFBL 1) regulates adventitious rooting through interactions with Aux/IAA28 in Populus.

Wenbo Shu,Meng‐Zhu Lu,Andrew Groover,Cheng Jiang,Zhangqi Yang,Shutang Zhao,Liuqiang Wang,Houjun Zhou,Quanzi Li

doi:10.1111/pbi.12980

Abstract

SummaryAdventitious roots occur naturally in many species and can also be induced from explants of some tree species including Populus, providing an important means of clonal propagation. Auxin has been identified as playing a crucial role in adventitious root formation, but the associated molecular regulatory mechanisms need to be elucidated. In this study, we examined the role of PagFBL1, the hybrid poplar (Populus alba × P. glandulosa clone 84K) homolog of Arabidopsis auxin receptor TIR1, in adventitious root formation in poplar. Similar to the distribution pattern of auxin during initiation of adventitious roots, PagFBL1 expression was concentrated in the cambium and secondary phloem in stems during adventitious root induction and initiation phases, but decreased in emerging adventitious root primordia. Overexpressing PagFBL1 stimulated adventitious root formation and increased root biomass, while knock‐down of PagFBL1 transcript levels delayed adventitious root formation and decreased root biomass. Transcriptome analyses of PagFBL1 overexpressing lines indicated that an extensive remodelling of gene expression was stimulated by auxin signalling pathway during early adventitious root formation. In addition, PagIAA28 was identified as downstream targets of PagFBL1. We propose that the PagFBL1‐PagIAA28 module promotes adventitious rooting and could be targeted to improve Populus propagation by cuttings.

Highlights

Roots play a crucial role in water and nutrient acquisition to support growth of the aerial parts of the plant, and healthy root systems contribute in maximizing plant biomass (Jansen et al, 2013)
We demonstrate that PagFBL1 is a key regulator in auxin signalling pathway to induce adventitious rooting, and the potential downstream regulators, including candidate Aux/indole-3-acetic acid (IAA) in the auxin signalling pathway, are identified in poplar
Three to four days after adventitious roots (ARs) induction, GUS signal was observed in the AR primordium which included cells within the cambial zone, secondary phloem and cortex (Figure 1e–h)

Summary

Introduction

Roots play a crucial role in water and nutrient acquisition to support growth of the aerial parts of the plant, and healthy root systems contribute in maximizing plant biomass (Jansen et al, 2013). ARs are produced during vegetative propagation by artificial induction using wounding or hormone application treatments in many dicotyledonous species (Nadkarni, 1994; Pacurar et al, 2014). The biological processes involved in AR formation are complex, and the temporal phases can be described as induction, initiation, activation of root primordium and out-growth (Legue et al, 2014). These processes are influenced by multiple factors, such as the genetic background and the physiological status of the mother plants, the application of hormones and environmental conditions (Geiss et al, 2010; Pacurar et al, 2014)

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Conclusion