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

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

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00719

DOI=10.3389/fpls.2015.00719

ISSN=1664-462X

ABSTRACT=<p>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 SCF<sup>TIR1/AFB</sup> and acts as an auxin co-receptor for nuclear auxin signaling. The SCF<sup>TIR1/AFB</sup>-proteasome machinery plays a central regulatory role in development-related gene transcription. <italic>Populus trichocarpa</italic>, 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 <italic>TIR1</italic> genes in the <italic>Populus</italic> genome that are phylogenetically clustered into four subgroups, <italic>PtrFBL1/PtrFBL2, PtrFBL3/PtrFBL4, PtrFBL5/PtrFBL6</italic>, and <italic>PtrFBL7/PtrFBL8</italic>, representing four paralogous pairs. In addition, the gene structure and motif composition were relatively conserved in each paralogous pair and all of the <italic>PtrFBL</italic> members were localized in the nucleus. Different sets of <italic>PtrFBLs</italic> were strongly expressed in the leaves, stems, roots, cambial zones, and immature xylem of <italic>Populus</italic>. Interestingly, <italic>PtrFBL1</italic> and <italic>7</italic> were expressed mainly in vascular and cambial tissues, respectively, indicating their potential but different roles in wood formation. Furthermore, <italic>Populus FBLs</italic> 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 <italic>PtrFBL</italic> genes in tree growth and development.</p>