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

Shu W, Liu Y, Guo Y, Zhou H, Zhang J, Zhao S, Lu M - Front Plant Sci (2015)

Bottom Line: Interestingly, PtrFBL1 and 7 were expressed mainly in vascular and cambial tissues, respectively, indicating their potential but different roles in wood formation.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.

View Article: PubMed Central - PubMed

Affiliation: Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University Nanjing, China ; State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry Beijing, China.

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 SCF(TIR1/AFB) and acts as an auxin co-receptor for nuclear auxin signaling. The SCF(TIR1/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.

No MeSH data available.


Related in: MedlinePlus

GUS assay of transgenic poplars driven by PtrFBL promoters. (A–F)PPtrFBL1::GUS: (A) 2-week-old seedling, (B) 4-week-old seedling, (C) root tip, (D) lateral root tip, and (E,F) GUS expressed mainly in stem; (G–J)PPtrFBL4::GUS: (G) 2-week-old seedling, (I) 4-week-old seedling, (H) root tip and (J) lateral root tip; (K–N)PPtrFBL5::GUS: (K) 2-week-old seedling, (M) 4-week-old seedling, (L) root tip, and (N) lateral root tip; (O–Q)PPtrFBL7::GUS: (O) 2-week-old seedling, (P) 4-week-old seedling, (Q) root tip and (R) lateral root tip; (S,T) GUS is expressed mainly in stems near the petiole. Bars, 1 cm (A–C,E,G,I,K,M,O,P,S), 2 mm (D,H,J,L,N,Q,R), 0.1 mm (F,T).
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Figure 3: GUS assay of transgenic poplars driven by PtrFBL promoters. (A–F)PPtrFBL1::GUS: (A) 2-week-old seedling, (B) 4-week-old seedling, (C) root tip, (D) lateral root tip, and (E,F) GUS expressed mainly in stem; (G–J)PPtrFBL4::GUS: (G) 2-week-old seedling, (I) 4-week-old seedling, (H) root tip and (J) lateral root tip; (K–N)PPtrFBL5::GUS: (K) 2-week-old seedling, (M) 4-week-old seedling, (L) root tip, and (N) lateral root tip; (O–Q)PPtrFBL7::GUS: (O) 2-week-old seedling, (P) 4-week-old seedling, (Q) root tip and (R) lateral root tip; (S,T) GUS is expressed mainly in stems near the petiole. Bars, 1 cm (A–C,E,G,I,K,M,O,P,S), 2 mm (D,H,J,L,N,Q,R), 0.1 mm (F,T).

Mentions: To further confirm the expression patterns of the PtrFBL genes, four PtrFBLs with different expression patterns in different tissues were selected for analysis using a promoter::GUS assay. The transgenic poplars (P. alba × P. glandulosa) with PPtrFBL1::GUS, PPtrFBL4::GUS, PPtrFBL5::GUS and PPtrFBL7::GUS were obtained, and GUS assays of whole plants were performed. Similar to the expression observed in Arabidopsis, expression levels of these PtrFBLs were high in the young tissues but low in the older tissues (Figure 3). However, the expression levels varied in different organs and tissues. Except in young leaves, primary stems, roots and lateral root tips, PtrFBL1 was found to mainly express in vascular tissues abaxial and adaxial to the cambium (Figures 3E,F), in accordance with semi-quantitative PCR results (Figure 2I). PtrFBL7 was also observed to be highly expressed in the cambial zone (Figure 2I), but closer observations revealed the expression was restricted to the cambium in the stem sections (Figures 3S,T), in compensation to the area of vascular tissues uncovered by the PtrFBL1 expression. However, although GUS staining of the whole plants with PPtrFBL4::GUS and PPtrFBL5::GUS confirmed the general expression patterns of these genes (Figures 3G–N), the expression was present in root tips (Figures 3H,J,L,N) and absent in root vascular tissues. In Arabidopsis, the AtAFB1::GUS protein was abundant throughout the Arabidopsis seedling, while the accumulations of AtTIR1, AtAFB2, and AtAFB3 proteins were highly restricted to growing tissues, including root tips, leaf primordia, and shoot meristems (Dharmasiri et al., 2005b; Parry et al., 2009). Therefore, poplar PtrFBLs exhibited more diversified expression patterns in different tissues. For instance, the differential expression of PtrFBL1 and PtrFBL7 was observed in secondary vascular tissues (Figure 3). In addition, these two genes may play differential roles in the maintenance of cambial activity and its differentiation into vascular tissues by mediating different auxin signaling. This phenomenon could not be observed in Arabidopsis because it lacks secondary vascular tissues.


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

Shu W, Liu Y, Guo Y, Zhou H, Zhang J, Zhao S, Lu M - Front Plant Sci (2015)

GUS assay of transgenic poplars driven by PtrFBL promoters. (A–F)PPtrFBL1::GUS: (A) 2-week-old seedling, (B) 4-week-old seedling, (C) root tip, (D) lateral root tip, and (E,F) GUS expressed mainly in stem; (G–J)PPtrFBL4::GUS: (G) 2-week-old seedling, (I) 4-week-old seedling, (H) root tip and (J) lateral root tip; (K–N)PPtrFBL5::GUS: (K) 2-week-old seedling, (M) 4-week-old seedling, (L) root tip, and (N) lateral root tip; (O–Q)PPtrFBL7::GUS: (O) 2-week-old seedling, (P) 4-week-old seedling, (Q) root tip and (R) lateral root tip; (S,T) GUS is expressed mainly in stems near the petiole. Bars, 1 cm (A–C,E,G,I,K,M,O,P,S), 2 mm (D,H,J,L,N,Q,R), 0.1 mm (F,T).
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Related In: Results  -  Collection

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Figure 3: GUS assay of transgenic poplars driven by PtrFBL promoters. (A–F)PPtrFBL1::GUS: (A) 2-week-old seedling, (B) 4-week-old seedling, (C) root tip, (D) lateral root tip, and (E,F) GUS expressed mainly in stem; (G–J)PPtrFBL4::GUS: (G) 2-week-old seedling, (I) 4-week-old seedling, (H) root tip and (J) lateral root tip; (K–N)PPtrFBL5::GUS: (K) 2-week-old seedling, (M) 4-week-old seedling, (L) root tip, and (N) lateral root tip; (O–Q)PPtrFBL7::GUS: (O) 2-week-old seedling, (P) 4-week-old seedling, (Q) root tip and (R) lateral root tip; (S,T) GUS is expressed mainly in stems near the petiole. Bars, 1 cm (A–C,E,G,I,K,M,O,P,S), 2 mm (D,H,J,L,N,Q,R), 0.1 mm (F,T).
Mentions: To further confirm the expression patterns of the PtrFBL genes, four PtrFBLs with different expression patterns in different tissues were selected for analysis using a promoter::GUS assay. The transgenic poplars (P. alba × P. glandulosa) with PPtrFBL1::GUS, PPtrFBL4::GUS, PPtrFBL5::GUS and PPtrFBL7::GUS were obtained, and GUS assays of whole plants were performed. Similar to the expression observed in Arabidopsis, expression levels of these PtrFBLs were high in the young tissues but low in the older tissues (Figure 3). However, the expression levels varied in different organs and tissues. Except in young leaves, primary stems, roots and lateral root tips, PtrFBL1 was found to mainly express in vascular tissues abaxial and adaxial to the cambium (Figures 3E,F), in accordance with semi-quantitative PCR results (Figure 2I). PtrFBL7 was also observed to be highly expressed in the cambial zone (Figure 2I), but closer observations revealed the expression was restricted to the cambium in the stem sections (Figures 3S,T), in compensation to the area of vascular tissues uncovered by the PtrFBL1 expression. However, although GUS staining of the whole plants with PPtrFBL4::GUS and PPtrFBL5::GUS confirmed the general expression patterns of these genes (Figures 3G–N), the expression was present in root tips (Figures 3H,J,L,N) and absent in root vascular tissues. In Arabidopsis, the AtAFB1::GUS protein was abundant throughout the Arabidopsis seedling, while the accumulations of AtTIR1, AtAFB2, and AtAFB3 proteins were highly restricted to growing tissues, including root tips, leaf primordia, and shoot meristems (Dharmasiri et al., 2005b; Parry et al., 2009). Therefore, poplar PtrFBLs exhibited more diversified expression patterns in different tissues. For instance, the differential expression of PtrFBL1 and PtrFBL7 was observed in secondary vascular tissues (Figure 3). In addition, these two genes may play differential roles in the maintenance of cambial activity and its differentiation into vascular tissues by mediating different auxin signaling. This phenomenon could not be observed in Arabidopsis because it lacks secondary vascular tissues.

Bottom Line: Interestingly, PtrFBL1 and 7 were expressed mainly in vascular and cambial tissues, respectively, indicating their potential but different roles in wood formation.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.

View Article: PubMed Central - PubMed

Affiliation: Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University Nanjing, China ; State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry Beijing, China.

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 SCF(TIR1/AFB) and acts as an auxin co-receptor for nuclear auxin signaling. The SCF(TIR1/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.

No MeSH data available.


Related in: MedlinePlus