A Populus TIR1 gene family survey reveals differential expression patterns and responses to 1-naphthaleneacetic acid and stress treatments.

Wenbo Shu,Yingli Liu,Jin Zhang,Mengzhu Lu,Houjun Zhou,Shutang Zhao,Yinghua Guo

doi:10.3389/fpls.2015.00719

Abstract

The plant hormone auxin is a central regulator of plant growth. TRANSPORT INHIBITOR RESPONSE 1/AUXIN SIGNALING F-BOX (TIR1/AFB) is a component of the E3 ubiquitin ligase complex SCFTIR1/AFB and acts as an auxin co-receptor for nuclear auxin signaling. The SCFTIR1/AFB-proteasome machinery plays a central regulatory role in development-related gene transcription. Populus trichocarpa, as a model tree, has a unique fast-growth trait to which auxin signaling may contribute. However, no systematic analyses of the genome organization, gene structure, and expression of TIR1-like genes have been undertaken in this woody model plant. In this study, we identified a total of eight TIR1 genes in the Populus genome that are phylogenetically clustered into four subgroups, PtrFBL1/PtrFBL2, PtrFBL3/PtrFBL4, PtrFBL5/PtrFBL6, and PtrFBL7/PtrFBL8, representing four paralogous pairs. In addition, the gene structure and motif composition were relatively conserved in each paralogous pair and all of the PtrFBL members were localized in the nucleus. Different sets of PtrFBLs were strongly expressed in the leaves, stems, roots, cambial zones, and immature xylem of Populus. Interestingly, PtrFBL1 and 7 were expressed mainly in vascular and cambial tissues, respectively, indicating their potential but different roles in wood formation. Furthermore, Populus FBLs responded differentially upon exposure to various stresses. Finally, over-expression studies indicated a role of FBL1 in poplar stem growth and response to drought stress. Collectively, these observations lay the foundation for further investigations into the potential roles of PtrFBL genes in tree growth and development.

Highlights

Plant growth and development are largely influenced by the surrounding environment, which is mediated by different phytohormones through signaling pathways
Three receptor/co-receptor complexes involved in auxin signaling have been identified: two inside of the cell [SCFTRANSPORT INHIBITOR RESPONSE 1/AUXIN SIGNALING F−BOX (TI R1/AFB) and SCFS−PHASE KINASE−ASSOCIATED PROTEIN 2A (SKP 2A)] and one at the cell periphery, Auxin Binding Protein 1 (ABP1; Salehin et al, 2015)
Characteristics of the Tir1 Gene Family in Arabidopsis and Populus We have identified eight TIR1 homologous genes (PtrFBLs) in P. trichocarpa (Table S2)

Summary

Introduction

Plant growth and development are largely influenced by the surrounding environment, which is mediated by different phytohormones through signaling pathways. Six Arabidopsis TIR1/AFB receptors, interacting with 29 Aux/IAA and 23 ARF combinations, modulate precisely the specific gene expression profile in response to auxin signaling (Salehin et al, 2015). In this study, using Arabidopsis AtTIR1/AFB, we have identified PtrFBLs in the P. trichocarpa genome, and determined their structure, phylogenetic relationships and expression patterns.

Results

Conclusion