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TCP24 modulates secondary cell wall thickening and anther endothecium development.

Wang H, Mao Y, Yang J, He Y - Front Plant Sci (2015)

Bottom Line: Several genes linked to secondary cell wall biogenesis and thickening were down-regulated in these transgenic plants.By contrast, the inhibition of TCP24 using the ectopic expression of a TCP24-SRDX repressor fusion protein, or the silencing of TCP genes by miR319a overexpression, increased cell wall lignification and the enhanced secondary cell wall thickening.Our results suggest that TCP24 acts as an important regulator of secondary cell wall thickening and modulates anther endothecium development.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences Shanghai, China.

ABSTRACT
miR319-targeted TCP genes are believed to regulate cell division in leaves and floral organs. However, it remains unknown whether these genes are involved in cell wall development. Here, we report that TCP24 negatively regulates secondary wall thickening in floral organs and roots. The overexpression of the miR319a-resistant version of TCP24 in Arabidopsis disrupted the thickening of secondary cell walls in the anther endothecium, leading to male sterility because of arrested anther dehiscence and pollen release. Several genes linked to secondary cell wall biogenesis and thickening were down-regulated in these transgenic plants. By contrast, the inhibition of TCP24 using the ectopic expression of a TCP24-SRDX repressor fusion protein, or the silencing of TCP genes by miR319a overexpression, increased cell wall lignification and the enhanced secondary cell wall thickening. Our results suggest that TCP24 acts as an important regulator of secondary cell wall thickening and modulates anther endothecium development.

No MeSH data available.


Related in: MedlinePlus

The floral organs and anthers of the transgenic plants with pTCP24:mTCP24. (A) Diagram of pTCP24:mTCP24 construct. (B) Inflorescences of the wild type (left) and pTCP24:mTCP24 (24-5; right) plants. (C–E) Open flowers in the wild type (C), 24-2 (D) and 24-5 (E) lines. (F–H) Anthers in the wild type (F), 24-2 (G), and 24-5 (H) lines. (I–K) The wild type (I), 24-2 (J), and 24-5 (K) anthers with phloroglucinol staining. (L–N) The wild type (L), 24-2 (M), and 24-5 (N) anthers treated with clearing fluid. Images in the left of each figures is magnified from the red boxes. Black arrows indicate the thickened endothecium cells, and yellow arrowheads indicate no thickened endothecium cells. Scale bars: 1 cm in (B); 500 μm in (C–E); 200 μm in (F–K); 100 μm in (L–N).
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Figure 4: The floral organs and anthers of the transgenic plants with pTCP24:mTCP24. (A) Diagram of pTCP24:mTCP24 construct. (B) Inflorescences of the wild type (left) and pTCP24:mTCP24 (24-5; right) plants. (C–E) Open flowers in the wild type (C), 24-2 (D) and 24-5 (E) lines. (F–H) Anthers in the wild type (F), 24-2 (G), and 24-5 (H) lines. (I–K) The wild type (I), 24-2 (J), and 24-5 (K) anthers with phloroglucinol staining. (L–N) The wild type (L), 24-2 (M), and 24-5 (N) anthers treated with clearing fluid. Images in the left of each figures is magnified from the red boxes. Black arrows indicate the thickened endothecium cells, and yellow arrowheads indicate no thickened endothecium cells. Scale bars: 1 cm in (B); 500 μm in (C–E); 200 μm in (F–K); 100 μm in (L–N).

Mentions: To exclude the effect of the 35S promoter on ectopic expression, we expressed TCP24 under the control of its native promoter (2.7 kb 5′ upstream of the TCP24 transcriptional start site) (Figure 4A). Among the pTCP24:mTCP24 lines, some had a complete loss of fertility because seed set was not observed, while most showed a reduced fertility compared with the wild type (Figure 4B). In the transgenic line 24-2 which was sterile, there was no pollen on the stigmas, indicating that pollen grain release from the anthers was arrested (Figures 4C,D), and no pollen was observed being released from the anthers (Figures 4F,G). Under the microscope, a few pollen grains were found to be outside the stomium on 24-5 plants (Figures 4E,H). Using phloroglucinol staining, we observed no staining in the anthers of 24-2 plants (Figure 4J) and very weak red staining in the anthers of 24-5 plants (Figures 4I,K). The cell walls of the endothecium were thickened uniformly in the wild type (Figure 4L), but they were not observed in 24-2 anthers (Figure 4M). On the transgenic line 24-5 which had reduced fertility, secondary cell walls occurred in some positions (Figure 4N). These observations confirmed that the overexpression of TCP24 inhibited secondary wall thickening in the anther endothecium.


TCP24 modulates secondary cell wall thickening and anther endothecium development.

Wang H, Mao Y, Yang J, He Y - Front Plant Sci (2015)

The floral organs and anthers of the transgenic plants with pTCP24:mTCP24. (A) Diagram of pTCP24:mTCP24 construct. (B) Inflorescences of the wild type (left) and pTCP24:mTCP24 (24-5; right) plants. (C–E) Open flowers in the wild type (C), 24-2 (D) and 24-5 (E) lines. (F–H) Anthers in the wild type (F), 24-2 (G), and 24-5 (H) lines. (I–K) The wild type (I), 24-2 (J), and 24-5 (K) anthers with phloroglucinol staining. (L–N) The wild type (L), 24-2 (M), and 24-5 (N) anthers treated with clearing fluid. Images in the left of each figures is magnified from the red boxes. Black arrows indicate the thickened endothecium cells, and yellow arrowheads indicate no thickened endothecium cells. Scale bars: 1 cm in (B); 500 μm in (C–E); 200 μm in (F–K); 100 μm in (L–N).
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Figure 4: The floral organs and anthers of the transgenic plants with pTCP24:mTCP24. (A) Diagram of pTCP24:mTCP24 construct. (B) Inflorescences of the wild type (left) and pTCP24:mTCP24 (24-5; right) plants. (C–E) Open flowers in the wild type (C), 24-2 (D) and 24-5 (E) lines. (F–H) Anthers in the wild type (F), 24-2 (G), and 24-5 (H) lines. (I–K) The wild type (I), 24-2 (J), and 24-5 (K) anthers with phloroglucinol staining. (L–N) The wild type (L), 24-2 (M), and 24-5 (N) anthers treated with clearing fluid. Images in the left of each figures is magnified from the red boxes. Black arrows indicate the thickened endothecium cells, and yellow arrowheads indicate no thickened endothecium cells. Scale bars: 1 cm in (B); 500 μm in (C–E); 200 μm in (F–K); 100 μm in (L–N).
Mentions: To exclude the effect of the 35S promoter on ectopic expression, we expressed TCP24 under the control of its native promoter (2.7 kb 5′ upstream of the TCP24 transcriptional start site) (Figure 4A). Among the pTCP24:mTCP24 lines, some had a complete loss of fertility because seed set was not observed, while most showed a reduced fertility compared with the wild type (Figure 4B). In the transgenic line 24-2 which was sterile, there was no pollen on the stigmas, indicating that pollen grain release from the anthers was arrested (Figures 4C,D), and no pollen was observed being released from the anthers (Figures 4F,G). Under the microscope, a few pollen grains were found to be outside the stomium on 24-5 plants (Figures 4E,H). Using phloroglucinol staining, we observed no staining in the anthers of 24-2 plants (Figure 4J) and very weak red staining in the anthers of 24-5 plants (Figures 4I,K). The cell walls of the endothecium were thickened uniformly in the wild type (Figure 4L), but they were not observed in 24-2 anthers (Figure 4M). On the transgenic line 24-5 which had reduced fertility, secondary cell walls occurred in some positions (Figure 4N). These observations confirmed that the overexpression of TCP24 inhibited secondary wall thickening in the anther endothecium.

Bottom Line: Several genes linked to secondary cell wall biogenesis and thickening were down-regulated in these transgenic plants.By contrast, the inhibition of TCP24 using the ectopic expression of a TCP24-SRDX repressor fusion protein, or the silencing of TCP genes by miR319a overexpression, increased cell wall lignification and the enhanced secondary cell wall thickening.Our results suggest that TCP24 acts as an important regulator of secondary cell wall thickening and modulates anther endothecium development.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences Shanghai, China.

ABSTRACT
miR319-targeted TCP genes are believed to regulate cell division in leaves and floral organs. However, it remains unknown whether these genes are involved in cell wall development. Here, we report that TCP24 negatively regulates secondary wall thickening in floral organs and roots. The overexpression of the miR319a-resistant version of TCP24 in Arabidopsis disrupted the thickening of secondary cell walls in the anther endothecium, leading to male sterility because of arrested anther dehiscence and pollen release. Several genes linked to secondary cell wall biogenesis and thickening were down-regulated in these transgenic plants. By contrast, the inhibition of TCP24 using the ectopic expression of a TCP24-SRDX repressor fusion protein, or the silencing of TCP genes by miR319a overexpression, increased cell wall lignification and the enhanced secondary cell wall thickening. Our results suggest that TCP24 acts as an important regulator of secondary cell wall thickening and modulates anther endothecium development.

No MeSH data available.


Related in: MedlinePlus