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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

UGGT activity is reduced in plants bearing mutations in the At1g71220 gene. a UGGT activity detection in A. thaliana ER-enriched fractions from wild type and mutant plants. Incorporation of UDP-[14C]-glucose into unfolded SBA by wild type or mutant ER fractions. The upper panel shows the radioactivity associated with SBA while the lower panel shows the total amount of SBA used in the assay. b Quantification of the UGGT activity obtained from the PhosphorImager scans presented in a
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Fig2: UGGT activity is reduced in plants bearing mutations in the At1g71220 gene. a UGGT activity detection in A. thaliana ER-enriched fractions from wild type and mutant plants. Incorporation of UDP-[14C]-glucose into unfolded SBA by wild type or mutant ER fractions. The upper panel shows the radioactivity associated with SBA while the lower panel shows the total amount of SBA used in the assay. b Quantification of the UGGT activity obtained from the PhosphorImager scans presented in a

Mentions: To confirm that At1g71220 is indeed responsible for the UGGT activity detected on ER-enriched fractions, we analyzed whether mutants in this gene have diminished UGGT activity. Two insertional mutants were identified: atuggt1-1 and atuggt1-2 (Additional file 4). Homozygous plants were obtained for both alleles (Additional file 4). Gene expression analyses by quantitative PCR showed that both UGGT-coding mutant alleles have decreased mRNA transcript levels; however, these were not completely abolished (Additional file 4). To determine whether the mutants had less UGGT activity we incubated ER-enriched fractions with denatured SBA and UDP-[14C]glucose. After the reaction, proteins were separated on SDS-PAGE, and the radioactivity associated with SBA was assessed. The results indicated that atuggt1-1 had some residual activity, whereas atuggt1-2 had no detectable re-glucosylation activity (Fig. 2). These results strongly suggest that At1g71220 is responsible for the UGGT activity in Arabidopsis.Fig. 2


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)

UGGT activity is reduced in plants bearing mutations in the At1g71220 gene. a UGGT activity detection in A. thaliana ER-enriched fractions from wild type and mutant plants. Incorporation of UDP-[14C]-glucose into unfolded SBA by wild type or mutant ER fractions. The upper panel shows the radioactivity associated with SBA while the lower panel shows the total amount of SBA used in the assay. b Quantification of the UGGT activity obtained from the PhosphorImager scans presented in a
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig2: UGGT activity is reduced in plants bearing mutations in the At1g71220 gene. a UGGT activity detection in A. thaliana ER-enriched fractions from wild type and mutant plants. Incorporation of UDP-[14C]-glucose into unfolded SBA by wild type or mutant ER fractions. The upper panel shows the radioactivity associated with SBA while the lower panel shows the total amount of SBA used in the assay. b Quantification of the UGGT activity obtained from the PhosphorImager scans presented in a
Mentions: To confirm that At1g71220 is indeed responsible for the UGGT activity detected on ER-enriched fractions, we analyzed whether mutants in this gene have diminished UGGT activity. Two insertional mutants were identified: atuggt1-1 and atuggt1-2 (Additional file 4). Homozygous plants were obtained for both alleles (Additional file 4). Gene expression analyses by quantitative PCR showed that both UGGT-coding mutant alleles have decreased mRNA transcript levels; however, these were not completely abolished (Additional file 4). To determine whether the mutants had less UGGT activity we incubated ER-enriched fractions with denatured SBA and UDP-[14C]glucose. After the reaction, proteins were separated on SDS-PAGE, and the radioactivity associated with SBA was assessed. The results indicated that atuggt1-1 had some residual activity, whereas atuggt1-2 had no detectable re-glucosylation activity (Fig. 2). These results strongly suggest that At1g71220 is responsible for the UGGT activity in Arabidopsis.Fig. 2

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