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Low temperature-induced DNA hypermethylation attenuates expression of RhAG, an AGAMOUS homolog, and increases petal number in rose (Rosa hybrida).

Ma N, Chen W, Fan T, Tian Y, Zhang S, Zeng D, Li Y - BMC Plant Biol. (2015)

Bottom Line: Quantitative RT-PCR analysis revealed that the expression pattern of RhAG, a rose homolog of the Arabidopsis thaliana AGAMOUS C-function gene, is associated with low temperature regulated flower development.Our results provide highlights in the role of RhAG gene in petal number determination and add a new layer of complexity in the regulation of floral organ development.We propose that RhAG plays an essential role in rose flower patterning by regulating petal development, and that low temperatures increase petal number, at least in part, by suppressing RhAG expression via enhancing DNA CHH hypermethylation of the RhAG promoter.

View Article: PubMed Central - PubMed

Affiliation: Department of Ornamental Horticulture, China Agricultural University, Beijing, 100193, China. ma_nan@cau.edu.cn.

ABSTRACT

Background: Flower development is central to angiosperm reproduction and is regulated by a broad range of endogenous and exogenous stimuli. It has been well documented that ambient temperature plays a key role in controlling flowering time; however, the mechanisms by which temperature regulates floral organ differentiation remain largely unknown.

Results: In this study, we show that low temperature treatment significantly increases petal number in rose (Rosa hybrida) through the promotion of stamen petaloidy. Quantitative RT-PCR analysis revealed that the expression pattern of RhAG, a rose homolog of the Arabidopsis thaliana AGAMOUS C-function gene, is associated with low temperature regulated flower development. Silencing of RhAG mimicked the impact of low temperature treatments on petal development by significantly increasing petal number through an increased production of petaloid stamens. In situ hybridization studies further revealed that low temperature restricts its spatial expression area. Analysis of DNA methylation level showed that low temperature treatment enhances the methylation level of the RhAG promoter, and a specific promoter region that was hypermethylated at CHH loci under low temperature conditions, was identified by bisulfite sequencing. This suggests that epigenetic DNA methylation contributes to the ambient temperature modulation of RhAG expression.

Discussion: Our results provide highlights in the role of RhAG gene in petal number determination and add a new layer of complexity in the regulation of floral organ development.

Conclusions: We propose that RhAG plays an essential role in rose flower patterning by regulating petal development, and that low temperatures increase petal number, at least in part, by suppressing RhAG expression via enhancing DNA CHH hypermethylation of the RhAG promoter.

No MeSH data available.


Related in: MedlinePlus

In situ hybridization of RhAG mRNA accumulation in rose flower buds. RhAG was detected using a DIG-labeled probe in flower buds of rose plants grown under normal temperature (25/15 °C) (a-f) or low temperature (15/5 °C) (g-l) conditions. a and g, stage 1 floral buds; b and h, stage 2 floral buds; c and i, stage 3 floral buds; d and j, stage 4 floral buds. A sense probe was used for stage 3 (e and k) and stage 4 (f and l) buds as a negative control. SE, sepal; PE, petal; ST, stamen; CA, carpel. Arrows show the boundary between petal and stamen. Scale bars = 100 μm (a, b, g and h) or 200 μm (c-f; i-l)
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Fig4: In situ hybridization of RhAG mRNA accumulation in rose flower buds. RhAG was detected using a DIG-labeled probe in flower buds of rose plants grown under normal temperature (25/15 °C) (a-f) or low temperature (15/5 °C) (g-l) conditions. a and g, stage 1 floral buds; b and h, stage 2 floral buds; c and i, stage 3 floral buds; d and j, stage 4 floral buds. A sense probe was used for stage 3 (e and k) and stage 4 (f and l) buds as a negative control. SE, sepal; PE, petal; ST, stamen; CA, carpel. Arrows show the boundary between petal and stamen. Scale bars = 100 μm (a, b, g and h) or 200 μm (c-f; i-l)

Mentions: To further confirm the proposed role of RhAG in the regulation of flower development, we examined its expression pattern in the floral primordia of low temperature treated flowers by in situ hybridization. As expected, irrespective of the ambient temperature regime or development stage, the expression of RhAG was undetectable in whorls 1 and 2 (Fig. 4a-d and g-j), while a persistent signal was detected in whorls 3 and 4 once they emerged (Fig. 4c, d, i, and j), consistent with previous reports [23]. Interestingly, we observed that the expression pattern was different at stage 4 between low-temperature treated buds and controls. In low-temperature treated buds, which developed more petal primordia, the expression area of RhAG was restricted towards the center of the meristem, which might give rise to the fourth whorl, and extended slightly to the lateral area where only a few stamen primordia emerged (Fig. 4j). In control flowers, the RhAG signal extended to a wider domain of whorl 3, from which many stamen primordia emerged (Fig. 4d). The reduced expression area supported the data obtained by quantitative RT-PCR and further suggested that the restricted expression of RhAG caused by the low temperature treatments might promote the petaloidy of stamens, resulting in the formation of double flowers.Fig. 4


Low temperature-induced DNA hypermethylation attenuates expression of RhAG, an AGAMOUS homolog, and increases petal number in rose (Rosa hybrida).

Ma N, Chen W, Fan T, Tian Y, Zhang S, Zeng D, Li Y - BMC Plant Biol. (2015)

In situ hybridization of RhAG mRNA accumulation in rose flower buds. RhAG was detected using a DIG-labeled probe in flower buds of rose plants grown under normal temperature (25/15 °C) (a-f) or low temperature (15/5 °C) (g-l) conditions. a and g, stage 1 floral buds; b and h, stage 2 floral buds; c and i, stage 3 floral buds; d and j, stage 4 floral buds. A sense probe was used for stage 3 (e and k) and stage 4 (f and l) buds as a negative control. SE, sepal; PE, petal; ST, stamen; CA, carpel. Arrows show the boundary between petal and stamen. Scale bars = 100 μm (a, b, g and h) or 200 μm (c-f; i-l)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4595006&req=5

Fig4: In situ hybridization of RhAG mRNA accumulation in rose flower buds. RhAG was detected using a DIG-labeled probe in flower buds of rose plants grown under normal temperature (25/15 °C) (a-f) or low temperature (15/5 °C) (g-l) conditions. a and g, stage 1 floral buds; b and h, stage 2 floral buds; c and i, stage 3 floral buds; d and j, stage 4 floral buds. A sense probe was used for stage 3 (e and k) and stage 4 (f and l) buds as a negative control. SE, sepal; PE, petal; ST, stamen; CA, carpel. Arrows show the boundary between petal and stamen. Scale bars = 100 μm (a, b, g and h) or 200 μm (c-f; i-l)
Mentions: To further confirm the proposed role of RhAG in the regulation of flower development, we examined its expression pattern in the floral primordia of low temperature treated flowers by in situ hybridization. As expected, irrespective of the ambient temperature regime or development stage, the expression of RhAG was undetectable in whorls 1 and 2 (Fig. 4a-d and g-j), while a persistent signal was detected in whorls 3 and 4 once they emerged (Fig. 4c, d, i, and j), consistent with previous reports [23]. Interestingly, we observed that the expression pattern was different at stage 4 between low-temperature treated buds and controls. In low-temperature treated buds, which developed more petal primordia, the expression area of RhAG was restricted towards the center of the meristem, which might give rise to the fourth whorl, and extended slightly to the lateral area where only a few stamen primordia emerged (Fig. 4j). In control flowers, the RhAG signal extended to a wider domain of whorl 3, from which many stamen primordia emerged (Fig. 4d). The reduced expression area supported the data obtained by quantitative RT-PCR and further suggested that the restricted expression of RhAG caused by the low temperature treatments might promote the petaloidy of stamens, resulting in the formation of double flowers.Fig. 4

Bottom Line: Quantitative RT-PCR analysis revealed that the expression pattern of RhAG, a rose homolog of the Arabidopsis thaliana AGAMOUS C-function gene, is associated with low temperature regulated flower development.Our results provide highlights in the role of RhAG gene in petal number determination and add a new layer of complexity in the regulation of floral organ development.We propose that RhAG plays an essential role in rose flower patterning by regulating petal development, and that low temperatures increase petal number, at least in part, by suppressing RhAG expression via enhancing DNA CHH hypermethylation of the RhAG promoter.

View Article: PubMed Central - PubMed

Affiliation: Department of Ornamental Horticulture, China Agricultural University, Beijing, 100193, China. ma_nan@cau.edu.cn.

ABSTRACT

Background: Flower development is central to angiosperm reproduction and is regulated by a broad range of endogenous and exogenous stimuli. It has been well documented that ambient temperature plays a key role in controlling flowering time; however, the mechanisms by which temperature regulates floral organ differentiation remain largely unknown.

Results: In this study, we show that low temperature treatment significantly increases petal number in rose (Rosa hybrida) through the promotion of stamen petaloidy. Quantitative RT-PCR analysis revealed that the expression pattern of RhAG, a rose homolog of the Arabidopsis thaliana AGAMOUS C-function gene, is associated with low temperature regulated flower development. Silencing of RhAG mimicked the impact of low temperature treatments on petal development by significantly increasing petal number through an increased production of petaloid stamens. In situ hybridization studies further revealed that low temperature restricts its spatial expression area. Analysis of DNA methylation level showed that low temperature treatment enhances the methylation level of the RhAG promoter, and a specific promoter region that was hypermethylated at CHH loci under low temperature conditions, was identified by bisulfite sequencing. This suggests that epigenetic DNA methylation contributes to the ambient temperature modulation of RhAG expression.

Discussion: Our results provide highlights in the role of RhAG gene in petal number determination and add a new layer of complexity in the regulation of floral organ development.

Conclusions: We propose that RhAG plays an essential role in rose flower patterning by regulating petal development, and that low temperatures increase petal number, at least in part, by suppressing RhAG expression via enhancing DNA CHH hypermethylation of the RhAG promoter.

No MeSH data available.


Related in: MedlinePlus