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The UDP-glucose: glycoprotein glucosyltransferase (UGGT), a key enzyme in ER quality control, plays a significant role in plant growth as well as biotic and abiotic stress in Arabidopsis thaliana.

Blanco-Herrera F, Moreno AA, Tapia R, Reyes F, Araya M, D'Alessio C, Parodi A, Orellana A - BMC Plant Biol. (2015)

Bottom Line: Here, we show that two mutant alleles in the At1g71220 locus have none or reduced UGGT activity.These results show that a lack of UGGT activity alters plant vegetative development and impairs the response to several abiotic and biotic stresses.Moreover, our results uncover an unexpected role of UGGT in the incorporation of UDP-Glucose into the ER lumen in Arabidopsis thaliana.

View Article: PubMed Central - PubMed

Affiliation: Centro de Biotecnología Vegetal, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Avenida República 217, Santiago, 837-0146, RM, Chile. mblanco@unab.cl.

ABSTRACT

Background: UDP-glucose: glycoprotein glucosyltransferase (UGGT) is a key player in the quality control mechanism (ER-QC) that newly synthesized glycoproteins undergo in the ER. It has been shown that the UGGT Arabidopsis orthologue is involved in ER-QC; however, its role in plant physiology remains unclear.

Results: Here, we show that two mutant alleles in the At1g71220 locus have none or reduced UGGT activity. In wild type plants, the AtUGGT transcript levels increased upon activation of the unfolded protein response (UPR). Interestingly, mutants in AtUGGT exhibited an endogenous up-regulation of genes that are UPR targets. In addition, mutants in AtUGGT showed a 30% reduction in the incorporation of UDP-Glucose into the ER suggesting that this enzyme drives the uptake of this substrate for the CNX/CRT cycle. Plants deficient in UGGT exhibited a delayed growth rate of the primary root and rosette as well as an alteration in the number of leaves. These mutants are more sensitive to pathogen attack as well as heat, salt, and UPR-inducing stressors. Additionally, the plants showed impairment in the establishment of systemic acquired resistance (SAR).

Conclusions: These results show that a lack of UGGT activity alters plant vegetative development and impairs the response to several abiotic and biotic stresses. Moreover, our results uncover an unexpected role of UGGT in the incorporation of UDP-Glucose into the ER lumen in Arabidopsis thaliana.

No MeSH data available.


Related in: MedlinePlus

The atuggt1-1 and atuggt1-2 mutants exhibit a reduced uptake of UDP-[14C]Glc into ER-derived vesicles. The UDP-Glc uptake was assayed into 50 μg of ER-enriched fractions from wild-type and AtUGGT mutant plants incubated with 1 μM UDP-[14C]Glc for 15 min. The reaction was stopped with a 10-fold dilution with cold STM buffer and filtration. The filter-associated label was counted using liquid scintillation. Results are presented as mean with SD; significance was determined with ANOVA. Asterisks indicate a Tukey’s test p-value < 0.001
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Fig4: The atuggt1-1 and atuggt1-2 mutants exhibit a reduced uptake of UDP-[14C]Glc into ER-derived vesicles. The UDP-Glc uptake was assayed into 50 μg of ER-enriched fractions from wild-type and AtUGGT mutant plants incubated with 1 μM UDP-[14C]Glc for 15 min. The reaction was stopped with a 10-fold dilution with cold STM buffer and filtration. The filter-associated label was counted using liquid scintillation. Results are presented as mean with SD; significance was determined with ANOVA. Asterisks indicate a Tukey’s test p-value < 0.001

Mentions: UDP-glucose is utilized by UGGT to re-glucosylate unfolded proteins within the ER. Our results showed that the UDP-glucose transporter gene AtUTr1 is up-regulated upon ER-stress induction, but that it is also endogenously up-regulated in cells lacking UGGT. The up-regulation of the transporter suggests that the uptake of UDP-glucose could be enhanced in AtUGGT mutants. However, the lack of glucosyltransferase in the ER should reduce the usage of UDP-glucose in the ER and lead to a lower incorporation of UDP-glucose into this organelle. To address this issue, we assessed the incorporation of UDP-glucose into ER-enriched fractions from both wild type and AtUGGT mutant plants. Fig. 4 shows that although the nucleotide-sugar transporter coding-gene is up regulated in both UGGT mutant alleles, these plants show a decrease in the incorporation of UDP-Glc into ER fractions. This indicates that an active UGGT is important to drive the uptake of its substrate.Fig. 4


The UDP-glucose: glycoprotein glucosyltransferase (UGGT), a key enzyme in ER quality control, plays a significant role in plant growth as well as biotic and abiotic stress in Arabidopsis thaliana.

Blanco-Herrera F, Moreno AA, Tapia R, Reyes F, Araya M, D'Alessio C, Parodi A, Orellana A - BMC Plant Biol. (2015)

The atuggt1-1 and atuggt1-2 mutants exhibit a reduced uptake of UDP-[14C]Glc into ER-derived vesicles. The UDP-Glc uptake was assayed into 50 μg of ER-enriched fractions from wild-type and AtUGGT mutant plants incubated with 1 μM UDP-[14C]Glc for 15 min. The reaction was stopped with a 10-fold dilution with cold STM buffer and filtration. The filter-associated label was counted using liquid scintillation. Results are presented as mean with SD; significance was determined with ANOVA. Asterisks indicate a Tukey’s test p-value < 0.001
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4465474&req=5

Fig4: The atuggt1-1 and atuggt1-2 mutants exhibit a reduced uptake of UDP-[14C]Glc into ER-derived vesicles. The UDP-Glc uptake was assayed into 50 μg of ER-enriched fractions from wild-type and AtUGGT mutant plants incubated with 1 μM UDP-[14C]Glc for 15 min. The reaction was stopped with a 10-fold dilution with cold STM buffer and filtration. The filter-associated label was counted using liquid scintillation. Results are presented as mean with SD; significance was determined with ANOVA. Asterisks indicate a Tukey’s test p-value < 0.001
Mentions: UDP-glucose is utilized by UGGT to re-glucosylate unfolded proteins within the ER. Our results showed that the UDP-glucose transporter gene AtUTr1 is up-regulated upon ER-stress induction, but that it is also endogenously up-regulated in cells lacking UGGT. The up-regulation of the transporter suggests that the uptake of UDP-glucose could be enhanced in AtUGGT mutants. However, the lack of glucosyltransferase in the ER should reduce the usage of UDP-glucose in the ER and lead to a lower incorporation of UDP-glucose into this organelle. To address this issue, we assessed the incorporation of UDP-glucose into ER-enriched fractions from both wild type and AtUGGT mutant plants. Fig. 4 shows that although the nucleotide-sugar transporter coding-gene is up regulated in both UGGT mutant alleles, these plants show a decrease in the incorporation of UDP-Glc into ER fractions. This indicates that an active UGGT is important to drive the uptake of its substrate.Fig. 4

Bottom Line: Here, we show that two mutant alleles in the At1g71220 locus have none or reduced UGGT activity.These results show that a lack of UGGT activity alters plant vegetative development and impairs the response to several abiotic and biotic stresses.Moreover, our results uncover an unexpected role of UGGT in the incorporation of UDP-Glucose into the ER lumen in Arabidopsis thaliana.

View Article: PubMed Central - PubMed

Affiliation: Centro de Biotecnología Vegetal, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Avenida República 217, Santiago, 837-0146, RM, Chile. mblanco@unab.cl.

ABSTRACT

Background: UDP-glucose: glycoprotein glucosyltransferase (UGGT) is a key player in the quality control mechanism (ER-QC) that newly synthesized glycoproteins undergo in the ER. It has been shown that the UGGT Arabidopsis orthologue is involved in ER-QC; however, its role in plant physiology remains unclear.

Results: Here, we show that two mutant alleles in the At1g71220 locus have none or reduced UGGT activity. In wild type plants, the AtUGGT transcript levels increased upon activation of the unfolded protein response (UPR). Interestingly, mutants in AtUGGT exhibited an endogenous up-regulation of genes that are UPR targets. In addition, mutants in AtUGGT showed a 30% reduction in the incorporation of UDP-Glucose into the ER suggesting that this enzyme drives the uptake of this substrate for the CNX/CRT cycle. Plants deficient in UGGT exhibited a delayed growth rate of the primary root and rosette as well as an alteration in the number of leaves. These mutants are more sensitive to pathogen attack as well as heat, salt, and UPR-inducing stressors. Additionally, the plants showed impairment in the establishment of systemic acquired resistance (SAR).

Conclusions: These results show that a lack of UGGT activity alters plant vegetative development and impairs the response to several abiotic and biotic stresses. Moreover, our results uncover an unexpected role of UGGT in the incorporation of UDP-Glucose into the ER lumen in Arabidopsis thaliana.

No MeSH data available.


Related in: MedlinePlus