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Eukaryotic release factor 1-2 affects Arabidopsis responses to glucose and phytohormones during germination and early seedling development.

Zhou X, Cooke P, Li L - J. Exp. Bot. (2009)

Bottom Line: The eRF1-2 gene was found to be specifically induced by glucose.By contrast, the loss-of-function erf1-2 mutant exhibited resistance to paclobutrazol, suggesting that eRF1-2 may exert a negative effect on the GA signalling pathway.Collectively, these data provide evidence in support of a novel role of eRF1-2 in affecting glucose and phytohormone responses in modulating plant growth and development.

View Article: PubMed Central - PubMed

Affiliation: Robert W Holley Center for Agriculture and Health, U.S. Department of Agriculture-Agricultural Research Service, Cornell University, Ithaca, NY 14853, USA.

ABSTRACT
Germination and early seedling development are coordinately regulated by glucose and phytohormones such as ABA, GA, and ethylene. However, the molecules that affect plant responses to glucose and phytohormones remain to be fully elucidated. Eukaryotic release factor 1 (eRF1) is responsible for the recognition of the stop codons in mRNAs during protein synthesis. Accumulating evidence indicates that eRF1 functions in other processes in addition to translation termination. The physiological role of eRF1-2, a member of the eRF1 family, in Arabidopsis was examined here. The eRF1-2 gene was found to be specifically induced by glucose. Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. Such hypersensitivity to glucose was accompanied by a dramatic reduction of the expression of glucose-regulated genes, chlorophyll a/b binding protein and plastocyanin. The hypersensitive response was not due to the enhanced accumulation of ABA. In addition, the eRF1-2 overexpressing plants showed increased sensitivity to paclobutrazol, an inhibitor of GA biosynthesis, and exogenous GA restored their normal growth. By contrast, the loss-of-function erf1-2 mutant exhibited resistance to paclobutrazol, suggesting that eRF1-2 may exert a negative effect on the GA signalling pathway. Collectively, these data provide evidence in support of a novel role of eRF1-2 in affecting glucose and phytohormone responses in modulating plant growth and development.

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Transgenic Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. (A) Effect of glucose on the growth phenotype of plants with altered levels of eRF1-2 expression. Six-day-old seedlings grown on MS plates containing 0%, 5%, and 6% glucose, respectively. Approximately 30 seeds from each line were used in the assay. The experiments were repeated three times. (B, C) Germination rate and primary root length of Arabidopsis plants after 6 d of incubation at 24 °C. The data represent an average of 30 plants +SD. Asterisks indicate significantly different means (P <0.05). (D, E) qRT-PCR analysis of expression of CAB1 and PC in 6-d-old Arabidopsis seedlings. The open bar and black bar stand for the 0% and the 6% glucose treatment, respectively. (This figure is available in colour at JXB online.)
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fig3: Transgenic Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. (A) Effect of glucose on the growth phenotype of plants with altered levels of eRF1-2 expression. Six-day-old seedlings grown on MS plates containing 0%, 5%, and 6% glucose, respectively. Approximately 30 seeds from each line were used in the assay. The experiments were repeated three times. (B, C) Germination rate and primary root length of Arabidopsis plants after 6 d of incubation at 24 °C. The data represent an average of 30 plants +SD. Asterisks indicate significantly different means (P <0.05). (D, E) qRT-PCR analysis of expression of CAB1 and PC in 6-d-old Arabidopsis seedlings. The open bar and black bar stand for the 0% and the 6% glucose treatment, respectively. (This figure is available in colour at JXB online.)

Mentions: As shown in Fig. 3A, there was no difference in seed germination and early seedling development when the plants were grown in the medium containing no glucose. However, the germination rate of the overexpressing lines was reduced in the presence of 5% and 6% glucose compared with the wild-type plants (Fig. 3A). At 6% glucose, the eRF1-2 overexpressing lines had 25% seed germination, whereas wild-type seeds germinated 65% (Fig. 3B). The primary root length of these transgenic plants was shorter than that of the wild type when the medium contained more than 3% glucose (Fig. 3C). These results show that transgenic plants overexpressing eRF1-2 resulted in hypersensitivity to glucose. No significant difference between wild type and the erf1-2 mutant in response to glucose treatment was observed; indicating that knock-out of the single gene was not enough to affect the glucose response, possibly because of the functional redundancy among the three eRF1 family members. Double knockout lines of eRF1-2 and eRF1-3 were generated. Examination of their response to glucose treatment showed that they exhibited the same response as the eRF1-2 single mutant (data not shown). Extensive efforts were made to generate triple knockout lines but without success. This may be due to the essential role of eRF1 proteins in protein synthesis termination. Similarly, homozygous eRF1-1 cosuppression lines could not be obtained (Petsch et al., 2005).


Eukaryotic release factor 1-2 affects Arabidopsis responses to glucose and phytohormones during germination and early seedling development.

Zhou X, Cooke P, Li L - J. Exp. Bot. (2009)

Transgenic Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. (A) Effect of glucose on the growth phenotype of plants with altered levels of eRF1-2 expression. Six-day-old seedlings grown on MS plates containing 0%, 5%, and 6% glucose, respectively. Approximately 30 seeds from each line were used in the assay. The experiments were repeated three times. (B, C) Germination rate and primary root length of Arabidopsis plants after 6 d of incubation at 24 °C. The data represent an average of 30 plants +SD. Asterisks indicate significantly different means (P <0.05). (D, E) qRT-PCR analysis of expression of CAB1 and PC in 6-d-old Arabidopsis seedlings. The open bar and black bar stand for the 0% and the 6% glucose treatment, respectively. (This figure is available in colour at JXB online.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803205&req=5

fig3: Transgenic Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. (A) Effect of glucose on the growth phenotype of plants with altered levels of eRF1-2 expression. Six-day-old seedlings grown on MS plates containing 0%, 5%, and 6% glucose, respectively. Approximately 30 seeds from each line were used in the assay. The experiments were repeated three times. (B, C) Germination rate and primary root length of Arabidopsis plants after 6 d of incubation at 24 °C. The data represent an average of 30 plants +SD. Asterisks indicate significantly different means (P <0.05). (D, E) qRT-PCR analysis of expression of CAB1 and PC in 6-d-old Arabidopsis seedlings. The open bar and black bar stand for the 0% and the 6% glucose treatment, respectively. (This figure is available in colour at JXB online.)
Mentions: As shown in Fig. 3A, there was no difference in seed germination and early seedling development when the plants were grown in the medium containing no glucose. However, the germination rate of the overexpressing lines was reduced in the presence of 5% and 6% glucose compared with the wild-type plants (Fig. 3A). At 6% glucose, the eRF1-2 overexpressing lines had 25% seed germination, whereas wild-type seeds germinated 65% (Fig. 3B). The primary root length of these transgenic plants was shorter than that of the wild type when the medium contained more than 3% glucose (Fig. 3C). These results show that transgenic plants overexpressing eRF1-2 resulted in hypersensitivity to glucose. No significant difference between wild type and the erf1-2 mutant in response to glucose treatment was observed; indicating that knock-out of the single gene was not enough to affect the glucose response, possibly because of the functional redundancy among the three eRF1 family members. Double knockout lines of eRF1-2 and eRF1-3 were generated. Examination of their response to glucose treatment showed that they exhibited the same response as the eRF1-2 single mutant (data not shown). Extensive efforts were made to generate triple knockout lines but without success. This may be due to the essential role of eRF1 proteins in protein synthesis termination. Similarly, homozygous eRF1-1 cosuppression lines could not be obtained (Petsch et al., 2005).

Bottom Line: The eRF1-2 gene was found to be specifically induced by glucose.By contrast, the loss-of-function erf1-2 mutant exhibited resistance to paclobutrazol, suggesting that eRF1-2 may exert a negative effect on the GA signalling pathway.Collectively, these data provide evidence in support of a novel role of eRF1-2 in affecting glucose and phytohormone responses in modulating plant growth and development.

View Article: PubMed Central - PubMed

Affiliation: Robert W Holley Center for Agriculture and Health, U.S. Department of Agriculture-Agricultural Research Service, Cornell University, Ithaca, NY 14853, USA.

ABSTRACT
Germination and early seedling development are coordinately regulated by glucose and phytohormones such as ABA, GA, and ethylene. However, the molecules that affect plant responses to glucose and phytohormones remain to be fully elucidated. Eukaryotic release factor 1 (eRF1) is responsible for the recognition of the stop codons in mRNAs during protein synthesis. Accumulating evidence indicates that eRF1 functions in other processes in addition to translation termination. The physiological role of eRF1-2, a member of the eRF1 family, in Arabidopsis was examined here. The eRF1-2 gene was found to be specifically induced by glucose. Arabidopsis plants overexpressing eRF1-2 were hypersensitive to glucose during germination and early seedling development. Such hypersensitivity to glucose was accompanied by a dramatic reduction of the expression of glucose-regulated genes, chlorophyll a/b binding protein and plastocyanin. The hypersensitive response was not due to the enhanced accumulation of ABA. In addition, the eRF1-2 overexpressing plants showed increased sensitivity to paclobutrazol, an inhibitor of GA biosynthesis, and exogenous GA restored their normal growth. By contrast, the loss-of-function erf1-2 mutant exhibited resistance to paclobutrazol, suggesting that eRF1-2 may exert a negative effect on the GA signalling pathway. Collectively, these data provide evidence in support of a novel role of eRF1-2 in affecting glucose and phytohormone responses in modulating plant growth and development.

Show MeSH
Related in: MedlinePlus