Limits...
SDG2-mediated H3K4 methylation is required for proper Arabidopsis root growth and development.

Yao X, Feng H, Yu Y, Dong A, Shen WH - PLoS ONE (2013)

Bottom Line: Loss of SDG2 results in drastically reduced H3K4me3 levels in root SCN and differentiated cells and causes the loss of auxin gradient maximum in the root quiescent centre.Genetic interaction analysis reveals that SDG2 and CHROMATIN ASSEMBLY FACTOR-1 act synergistically in root SCN and genome integrity maintenance but not in telomere length maintenance.We conclude that SDG2-mediated H3K4me3 plays a distinctive role in the regulation of chromatin structure and genome integrity, which are key features in pluripotency of stem cells and crucial for root growth and development.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China.

ABSTRACT
Trithorax group (TrxG) proteins are evolutionarily conserved in eukaryotes and play critical roles in transcriptional activation via deposition of histone H3 lysine 4 trimethylation (H3K4me3) in chromatin. Several Arabidopsis TrxG members have been characterized, and among them SET DOMAIN GROUP 2 (SDG2) has been shown to be necessary for global genome-wide H3K4me3 deposition. Although pleiotropic phenotypes have been uncovered in the sdg2 mutants, SDG2 function in the regulation of stem cell activity has remained largely unclear. Here, we investigate the sdg2 mutant root phenotype and demonstrate that SDG2 is required for primary root stem cell niche (SCN) maintenance as well as for lateral root SCN establishment. Loss of SDG2 results in drastically reduced H3K4me3 levels in root SCN and differentiated cells and causes the loss of auxin gradient maximum in the root quiescent centre. Elevated DNA damage is detected in the sdg2 mutant, suggesting that impaired genome integrity may also have challenged the stem cell activity. Genetic interaction analysis reveals that SDG2 and CHROMATIN ASSEMBLY FACTOR-1 act synergistically in root SCN and genome integrity maintenance but not in telomere length maintenance. We conclude that SDG2-mediated H3K4me3 plays a distinctive role in the regulation of chromatin structure and genome integrity, which are key features in pluripotency of stem cells and crucial for root growth and development.

Show MeSH

Related in: MedlinePlus

Loss of SDG2 synergistically enhances growth defects of the CAF1 loss-of-function mutant fas2-4. A, Representative example of 14-day-old seedling of the wild-type Col, the single mutants sdg2-3 and fas2-4, and the double mutant sdg2-3 fas2-4. Bar = 1 cm. B, Comparison of primary root length between fas2-4 and sdg2-3 fas2-4 on 16-day-old seedlings. Root length is shown as a mean value from two independent experiments with each comprising at least 20 plants. Bar indicates SD. C and D, Comparison of root cap cell organization between fas2-4 and sdg2-3 fas2-4, respectively. DIC images were taken on Lugol-stained root tips of 6-day-old seedlings. Arrowhead in C indicates QC position. Bar = 50 µm. E and F, Comparison of cell layer organizations of root apical meristem between fas2-4 and sdg2-3 fas2-4, respectively. Confocal images were taken on PI-stained roots of 6-day-old seedlings. The QC cell in E is marked in blue. Bar = 50 µm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3585709&req=5

pone-0056537-g005: Loss of SDG2 synergistically enhances growth defects of the CAF1 loss-of-function mutant fas2-4. A, Representative example of 14-day-old seedling of the wild-type Col, the single mutants sdg2-3 and fas2-4, and the double mutant sdg2-3 fas2-4. Bar = 1 cm. B, Comparison of primary root length between fas2-4 and sdg2-3 fas2-4 on 16-day-old seedlings. Root length is shown as a mean value from two independent experiments with each comprising at least 20 plants. Bar indicates SD. C and D, Comparison of root cap cell organization between fas2-4 and sdg2-3 fas2-4, respectively. DIC images were taken on Lugol-stained root tips of 6-day-old seedlings. Arrowhead in C indicates QC position. Bar = 50 µm. E and F, Comparison of cell layer organizations of root apical meristem between fas2-4 and sdg2-3 fas2-4, respectively. Confocal images were taken on PI-stained roots of 6-day-old seedlings. The QC cell in E is marked in blue. Bar = 50 µm.

Mentions: CAF-1 regulates histone deposition in chromatin and the loss-of-CAF-1 mutants fas1 and fas2 exhibit multiple defects of root development, including loss of SCN [24], perturbed cell fate at epidermis [21], and compromised LR development [52]. We asked whether SDG2 and CAF-1 act in a same regulatory pathway. To address this question, we generated the sdg2-3 fas2-4 double mutant by genetic crosses between the sdg2-3 and fas2-4 single mutants. The double mutant showed a drastically arrested growth phenotype (Figure 5A). While the sdg2-3 and fas2-4 single mutants showed a similar short-root phenotype, a synergistic effect of sdg2-3 and fas2-4 on root growth inhibition was observed (Figure 5A and 5B). The mean root length of the double mutant sdg2-3 fas2-4 reached to less than 20% of that of fas2-4 at 16 days after germination (Figure 5B). The regular arrangement of the cell layers at RAM was disturbed in fas2-4 (Figure 5C and 5E), which is in agreement with the previous report on another mutant allele fas2-1[24]. Compared with the single mutant fas2-4 (Figure 5C), the double mutant sdg2-3 fas2-4 showed much fewer starch granules at the root tip cells (Figure 5D). The PI staining and microscopy analysis showed that the typical cellular organization of SCN was totally lost in sdg2-3 fas2-4 (Figure 5F). The severe disorganization and loss of SCN are consistent with the drastic root growth defects observed in sdg2-3 fas2-4. The synergistic effect of sdg2-3 and fas2-4 indicates that SDG2 and CAF-1 act in genetically parallel pathways and they are independently required for the maintenance of root SCN organization and stem cell activity.


SDG2-mediated H3K4 methylation is required for proper Arabidopsis root growth and development.

Yao X, Feng H, Yu Y, Dong A, Shen WH - PLoS ONE (2013)

Loss of SDG2 synergistically enhances growth defects of the CAF1 loss-of-function mutant fas2-4. A, Representative example of 14-day-old seedling of the wild-type Col, the single mutants sdg2-3 and fas2-4, and the double mutant sdg2-3 fas2-4. Bar = 1 cm. B, Comparison of primary root length between fas2-4 and sdg2-3 fas2-4 on 16-day-old seedlings. Root length is shown as a mean value from two independent experiments with each comprising at least 20 plants. Bar indicates SD. C and D, Comparison of root cap cell organization between fas2-4 and sdg2-3 fas2-4, respectively. DIC images were taken on Lugol-stained root tips of 6-day-old seedlings. Arrowhead in C indicates QC position. Bar = 50 µm. E and F, Comparison of cell layer organizations of root apical meristem between fas2-4 and sdg2-3 fas2-4, respectively. Confocal images were taken on PI-stained roots of 6-day-old seedlings. The QC cell in E is marked in blue. Bar = 50 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585709&req=5

pone-0056537-g005: Loss of SDG2 synergistically enhances growth defects of the CAF1 loss-of-function mutant fas2-4. A, Representative example of 14-day-old seedling of the wild-type Col, the single mutants sdg2-3 and fas2-4, and the double mutant sdg2-3 fas2-4. Bar = 1 cm. B, Comparison of primary root length between fas2-4 and sdg2-3 fas2-4 on 16-day-old seedlings. Root length is shown as a mean value from two independent experiments with each comprising at least 20 plants. Bar indicates SD. C and D, Comparison of root cap cell organization between fas2-4 and sdg2-3 fas2-4, respectively. DIC images were taken on Lugol-stained root tips of 6-day-old seedlings. Arrowhead in C indicates QC position. Bar = 50 µm. E and F, Comparison of cell layer organizations of root apical meristem between fas2-4 and sdg2-3 fas2-4, respectively. Confocal images were taken on PI-stained roots of 6-day-old seedlings. The QC cell in E is marked in blue. Bar = 50 µm.
Mentions: CAF-1 regulates histone deposition in chromatin and the loss-of-CAF-1 mutants fas1 and fas2 exhibit multiple defects of root development, including loss of SCN [24], perturbed cell fate at epidermis [21], and compromised LR development [52]. We asked whether SDG2 and CAF-1 act in a same regulatory pathway. To address this question, we generated the sdg2-3 fas2-4 double mutant by genetic crosses between the sdg2-3 and fas2-4 single mutants. The double mutant showed a drastically arrested growth phenotype (Figure 5A). While the sdg2-3 and fas2-4 single mutants showed a similar short-root phenotype, a synergistic effect of sdg2-3 and fas2-4 on root growth inhibition was observed (Figure 5A and 5B). The mean root length of the double mutant sdg2-3 fas2-4 reached to less than 20% of that of fas2-4 at 16 days after germination (Figure 5B). The regular arrangement of the cell layers at RAM was disturbed in fas2-4 (Figure 5C and 5E), which is in agreement with the previous report on another mutant allele fas2-1[24]. Compared with the single mutant fas2-4 (Figure 5C), the double mutant sdg2-3 fas2-4 showed much fewer starch granules at the root tip cells (Figure 5D). The PI staining and microscopy analysis showed that the typical cellular organization of SCN was totally lost in sdg2-3 fas2-4 (Figure 5F). The severe disorganization and loss of SCN are consistent with the drastic root growth defects observed in sdg2-3 fas2-4. The synergistic effect of sdg2-3 and fas2-4 indicates that SDG2 and CAF-1 act in genetically parallel pathways and they are independently required for the maintenance of root SCN organization and stem cell activity.

Bottom Line: Loss of SDG2 results in drastically reduced H3K4me3 levels in root SCN and differentiated cells and causes the loss of auxin gradient maximum in the root quiescent centre.Genetic interaction analysis reveals that SDG2 and CHROMATIN ASSEMBLY FACTOR-1 act synergistically in root SCN and genome integrity maintenance but not in telomere length maintenance.We conclude that SDG2-mediated H3K4me3 plays a distinctive role in the regulation of chromatin structure and genome integrity, which are key features in pluripotency of stem cells and crucial for root growth and development.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Genetic Engineering, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Fudan University, Shanghai, PR China.

ABSTRACT
Trithorax group (TrxG) proteins are evolutionarily conserved in eukaryotes and play critical roles in transcriptional activation via deposition of histone H3 lysine 4 trimethylation (H3K4me3) in chromatin. Several Arabidopsis TrxG members have been characterized, and among them SET DOMAIN GROUP 2 (SDG2) has been shown to be necessary for global genome-wide H3K4me3 deposition. Although pleiotropic phenotypes have been uncovered in the sdg2 mutants, SDG2 function in the regulation of stem cell activity has remained largely unclear. Here, we investigate the sdg2 mutant root phenotype and demonstrate that SDG2 is required for primary root stem cell niche (SCN) maintenance as well as for lateral root SCN establishment. Loss of SDG2 results in drastically reduced H3K4me3 levels in root SCN and differentiated cells and causes the loss of auxin gradient maximum in the root quiescent centre. Elevated DNA damage is detected in the sdg2 mutant, suggesting that impaired genome integrity may also have challenged the stem cell activity. Genetic interaction analysis reveals that SDG2 and CHROMATIN ASSEMBLY FACTOR-1 act synergistically in root SCN and genome integrity maintenance but not in telomere length maintenance. We conclude that SDG2-mediated H3K4me3 plays a distinctive role in the regulation of chromatin structure and genome integrity, which are key features in pluripotency of stem cells and crucial for root growth and development.

Show MeSH
Related in: MedlinePlus