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Developmentally early and late onset of Rps10 silencing in Arabidopsis thaliana: genetic and environmental regulation.

Majewski P, Wołoszyńska M, Jańska H - J. Exp. Bot. (2009)

Bottom Line: Transgene dosage, silencing competence of the transgene loci, and photoperiod conditions were found to regulate the onset and efficiency of Rps10 silencing in two independent transgenic lines of Arabidopsis thaliana.P1 plants either died during the vegetative growth phase or were rescued by reversion resulting from inactivation of silencing.The most severe and early was the P2 phenotype found in only one transgenic line and most probably resulting from high competence of the transgene loci.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Cell Biology, Faculty of Biotechnology, University of Wroclaw, ul. Przybyszewskiego 63/77, 51-148 Wroclaw, Poland.

ABSTRACT
Transgene dosage, silencing competence of the transgene loci, and photoperiod conditions were found to regulate the onset and efficiency of Rps10 silencing in two independent transgenic lines of Arabidopsis thaliana. The Rps10 gene encodes the S10 protein which is part of the small subunit of mitochondrial ribosomes. Homozygous plants presented developmentally early onset of silencing, a very efficient decrease in the level of Rps10 transcripts, as well as a severe and uniform phenotype called P1. P1 plants either died during the vegetative growth phase or were rescued by reversion resulting from inactivation of silencing. A wide variety of morphological and developmental abnormalities observed within the hemizygous transformants allowed their classification into three categories P2, P3, and P4. The most severe and early was the P2 phenotype found in only one transgenic line and most probably resulting from high competence of the transgene loci. Developmentally late onset of silencing occurred only in the short day photoperiod and was characteristic for the P3 and P4 plants. This phenomenon was attributed to conditions favourable to silencing achieved in the short day photoperiod, e.g. a greatly prolonged vegetative phase accompanied by a gradual increase of the level of Rps10 transcripts. To the best of our knowledge, this is the first report indicating that the onset of silencing depends on the photoperiod conditions in A. thaliana.

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Phenotype categories P1, P2, and P0 observed under the long day conditions in the Rps10.1 line. (A) Three phenotype categories observed in the third week of the vegetative growth phase. (B) Only the P2 and P0 phenotype categories are observed during the generative growth phase.
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fig6: Phenotype categories P1, P2, and P0 observed under the long day conditions in the Rps10.1 line. (A) Three phenotype categories observed in the third week of the vegetative growth phase. (B) Only the P2 and P0 phenotype categories are observed during the generative growth phase.

Mentions: The switch from the SD to the LD photoperiod resulted in a dramatic decrease in the proportion of plants showing altered phenotypes. Based on observations carried out over three generations, it was estimated that nearly half of the plants developed phenotypic abnormalities under LD conditions (Table 2B). These plants represented either P1 or P2 phenotype categories (Fig. 6). The remaining plants, which did not develop any phenotypic changes, although they were observed until the late reproductive growth phase, were named P0 (Table 2). It was not clear if the P0 plants showed the wild-type phenotype due to the lack of silencing or due to inefficient silencing. To discriminate between these two possibilities the levels of the Rps10 transcripts in the rosette leaves (Fig. 7A) and flowers (Fig. 7B) of 7-week-old P0, P2, and control plants were compared. The results clearly demonstrated that the Rps10 gene was silenced in both the rosette leaves and flowers of the P2 plants. However, any sign of silencing was found in the P0 plants, indicating that the LD conditions prevent the late onset of silencing. Thus, the SD photoperiod not only stimulated more transformants to develop the altered phenotype, but it also induced P3 and P4 phenotypes characteristic only for this photoperiod (Table 2). The loss of the late silencing in LD compared with SD conditions was shown to be statistically significant using Fisher's exact test (P=1.55×10−5 for T3; P=4.72×10−7 for T4; P=8.47×10−4 for T5). The decrease in the incidence of silencing-induced phenotype observed in LD versus SD conditions was also shown to be statistically significant (P=2.89×10−3 for T3; P=9.92×10−3 for T4; P=5.86×10−3 for T5).


Developmentally early and late onset of Rps10 silencing in Arabidopsis thaliana: genetic and environmental regulation.

Majewski P, Wołoszyńska M, Jańska H - J. Exp. Bot. (2009)

Phenotype categories P1, P2, and P0 observed under the long day conditions in the Rps10.1 line. (A) Three phenotype categories observed in the third week of the vegetative growth phase. (B) Only the P2 and P0 phenotype categories are observed during the generative growth phase.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2657537&req=5

fig6: Phenotype categories P1, P2, and P0 observed under the long day conditions in the Rps10.1 line. (A) Three phenotype categories observed in the third week of the vegetative growth phase. (B) Only the P2 and P0 phenotype categories are observed during the generative growth phase.
Mentions: The switch from the SD to the LD photoperiod resulted in a dramatic decrease in the proportion of plants showing altered phenotypes. Based on observations carried out over three generations, it was estimated that nearly half of the plants developed phenotypic abnormalities under LD conditions (Table 2B). These plants represented either P1 or P2 phenotype categories (Fig. 6). The remaining plants, which did not develop any phenotypic changes, although they were observed until the late reproductive growth phase, were named P0 (Table 2). It was not clear if the P0 plants showed the wild-type phenotype due to the lack of silencing or due to inefficient silencing. To discriminate between these two possibilities the levels of the Rps10 transcripts in the rosette leaves (Fig. 7A) and flowers (Fig. 7B) of 7-week-old P0, P2, and control plants were compared. The results clearly demonstrated that the Rps10 gene was silenced in both the rosette leaves and flowers of the P2 plants. However, any sign of silencing was found in the P0 plants, indicating that the LD conditions prevent the late onset of silencing. Thus, the SD photoperiod not only stimulated more transformants to develop the altered phenotype, but it also induced P3 and P4 phenotypes characteristic only for this photoperiod (Table 2). The loss of the late silencing in LD compared with SD conditions was shown to be statistically significant using Fisher's exact test (P=1.55×10−5 for T3; P=4.72×10−7 for T4; P=8.47×10−4 for T5). The decrease in the incidence of silencing-induced phenotype observed in LD versus SD conditions was also shown to be statistically significant (P=2.89×10−3 for T3; P=9.92×10−3 for T4; P=5.86×10−3 for T5).

Bottom Line: Transgene dosage, silencing competence of the transgene loci, and photoperiod conditions were found to regulate the onset and efficiency of Rps10 silencing in two independent transgenic lines of Arabidopsis thaliana.P1 plants either died during the vegetative growth phase or were rescued by reversion resulting from inactivation of silencing.The most severe and early was the P2 phenotype found in only one transgenic line and most probably resulting from high competence of the transgene loci.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Cell Biology, Faculty of Biotechnology, University of Wroclaw, ul. Przybyszewskiego 63/77, 51-148 Wroclaw, Poland.

ABSTRACT
Transgene dosage, silencing competence of the transgene loci, and photoperiod conditions were found to regulate the onset and efficiency of Rps10 silencing in two independent transgenic lines of Arabidopsis thaliana. The Rps10 gene encodes the S10 protein which is part of the small subunit of mitochondrial ribosomes. Homozygous plants presented developmentally early onset of silencing, a very efficient decrease in the level of Rps10 transcripts, as well as a severe and uniform phenotype called P1. P1 plants either died during the vegetative growth phase or were rescued by reversion resulting from inactivation of silencing. A wide variety of morphological and developmental abnormalities observed within the hemizygous transformants allowed their classification into three categories P2, P3, and P4. The most severe and early was the P2 phenotype found in only one transgenic line and most probably resulting from high competence of the transgene loci. Developmentally late onset of silencing occurred only in the short day photoperiod and was characteristic for the P3 and P4 plants. This phenomenon was attributed to conditions favourable to silencing achieved in the short day photoperiod, e.g. a greatly prolonged vegetative phase accompanied by a gradual increase of the level of Rps10 transcripts. To the best of our knowledge, this is the first report indicating that the onset of silencing depends on the photoperiod conditions in A. thaliana.

Show MeSH
Related in: MedlinePlus