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Loss of the Arabidopsis thaliana P₄-ATPase ALA3 reduces adaptability to temperature stresses and impairs vegetative, pollen, and ovule development.

McDowell SC, López-Marqués RL, Poulsen LR, Palmgren MG, Harper JF - PLoS ONE (2013)

Bottom Line: We also demonstrate that ala3 mutants have reduced fecundity resulting from a combination of decreased ovule production and pollen tube growth defects.In-vitro pollen tube growth assays showed that ala3 pollen germinated ∼2 h slower than wild-type and had approximately 2-fold reductions in both maximal growth rate and overall length.Together, these results support a model in which ALA3 functions to modify endomembranes in multiple cell types, enabling structural changes, or signaling functions that are critical in plants for normal development and adaptation to varied growth environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada, United States of America.

ABSTRACT
Members of the P4 subfamily of P-type ATPases are thought to help create asymmetry in lipid bilayers by flipping specific lipids between the leaflets of a membrane. This asymmetry is believed to be central to the formation of vesicles in the secretory and endocytic pathways. In Arabidopsis thaliana, a P4-ATPase associated with the trans-Golgi network (ALA3) was previously reported to be important for vegetative growth and reproductive success. Here we show that multiple phenotypes for ala3 knockouts are sensitive to growth conditions. For example, ala3 rosette size was observed to be dependent upon both temperature and soil, and varied between 40% and 80% that of wild-type under different conditions. We also demonstrate that ala3 mutants have reduced fecundity resulting from a combination of decreased ovule production and pollen tube growth defects. In-vitro pollen tube growth assays showed that ala3 pollen germinated ∼2 h slower than wild-type and had approximately 2-fold reductions in both maximal growth rate and overall length. In genetic crosses under conditions of hot days and cold nights, pollen fitness was reduced by at least 90-fold; from ∼18% transmission efficiency (unstressed) to less than 0.2% (stressed). Together, these results support a model in which ALA3 functions to modify endomembranes in multiple cell types, enabling structural changes, or signaling functions that are critical in plants for normal development and adaptation to varied growth environments.

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Loss of ALA3 results in reduced seed set with an uneven distribution of seed.(A) Representative examples of wild-type and ala3 siliques cleared with 70% EtOH to show seed positions. (B) Ovule number is reduced in ala3 pistils, but not sufficiently to account for the total reduction in seed set. Average results (±SE) are reported for two independent experiments, n = 14–18 pistils for ala3 mutants and n = 38 pistils for Col-0. Pistils were collected from a total of 5–6 different plants for each genotype. (C) Graph of seed set by sector. Siliques were divided into four sectors of equal length, with sector 1 at the top (stigma end) of the silique and sector 4 at the base of the silique. Average results (±SE) are reported for two independent experiments, n = 30–36 siliques. Siliques were collected from a total of 6–7 different plants for each genotype. Sector numbers appear below each column and the average total seed set for each genotype is given above the corresponding sector data. *Significantly different from wild-type (p<0.05, Welch’s t-test). a,b,cColumns sharing common labels (letters) are not significantly different from each other (p>0.05).
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pone-0062577-g005: Loss of ALA3 results in reduced seed set with an uneven distribution of seed.(A) Representative examples of wild-type and ala3 siliques cleared with 70% EtOH to show seed positions. (B) Ovule number is reduced in ala3 pistils, but not sufficiently to account for the total reduction in seed set. Average results (±SE) are reported for two independent experiments, n = 14–18 pistils for ala3 mutants and n = 38 pistils for Col-0. Pistils were collected from a total of 5–6 different plants for each genotype. (C) Graph of seed set by sector. Siliques were divided into four sectors of equal length, with sector 1 at the top (stigma end) of the silique and sector 4 at the base of the silique. Average results (±SE) are reported for two independent experiments, n = 30–36 siliques. Siliques were collected from a total of 6–7 different plants for each genotype. Sector numbers appear below each column and the average total seed set for each genotype is given above the corresponding sector data. *Significantly different from wild-type (p<0.05, Welch’s t-test). a,b,cColumns sharing common labels (letters) are not significantly different from each other (p>0.05).

Mentions: In homozygous ala3 mutants, seed set in each silique was decreased to ∼59% that of wild-type (Figure 5). A high frequency of empty seed positions were observed within ala3 siliques, the majority of which were near the bottom of the silique (Figure 5a, c). This uneven seed distribution was reversed by manual fertilization of ala3 pistils with wild-type pollen (Figure S3), consistent with the potential that homozygous plants either shed less pollen or have defective pollen. However, an explanation based on a pollen fitness problem is favored by in-vitro growth (Figure 4) and in-vivo competition (Table 2) assays, both of which indicate a pollen defect.


Loss of the Arabidopsis thaliana P₄-ATPase ALA3 reduces adaptability to temperature stresses and impairs vegetative, pollen, and ovule development.

McDowell SC, López-Marqués RL, Poulsen LR, Palmgren MG, Harper JF - PLoS ONE (2013)

Loss of ALA3 results in reduced seed set with an uneven distribution of seed.(A) Representative examples of wild-type and ala3 siliques cleared with 70% EtOH to show seed positions. (B) Ovule number is reduced in ala3 pistils, but not sufficiently to account for the total reduction in seed set. Average results (±SE) are reported for two independent experiments, n = 14–18 pistils for ala3 mutants and n = 38 pistils for Col-0. Pistils were collected from a total of 5–6 different plants for each genotype. (C) Graph of seed set by sector. Siliques were divided into four sectors of equal length, with sector 1 at the top (stigma end) of the silique and sector 4 at the base of the silique. Average results (±SE) are reported for two independent experiments, n = 30–36 siliques. Siliques were collected from a total of 6–7 different plants for each genotype. Sector numbers appear below each column and the average total seed set for each genotype is given above the corresponding sector data. *Significantly different from wild-type (p<0.05, Welch’s t-test). a,b,cColumns sharing common labels (letters) are not significantly different from each other (p>0.05).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3646830&req=5

pone-0062577-g005: Loss of ALA3 results in reduced seed set with an uneven distribution of seed.(A) Representative examples of wild-type and ala3 siliques cleared with 70% EtOH to show seed positions. (B) Ovule number is reduced in ala3 pistils, but not sufficiently to account for the total reduction in seed set. Average results (±SE) are reported for two independent experiments, n = 14–18 pistils for ala3 mutants and n = 38 pistils for Col-0. Pistils were collected from a total of 5–6 different plants for each genotype. (C) Graph of seed set by sector. Siliques were divided into four sectors of equal length, with sector 1 at the top (stigma end) of the silique and sector 4 at the base of the silique. Average results (±SE) are reported for two independent experiments, n = 30–36 siliques. Siliques were collected from a total of 6–7 different plants for each genotype. Sector numbers appear below each column and the average total seed set for each genotype is given above the corresponding sector data. *Significantly different from wild-type (p<0.05, Welch’s t-test). a,b,cColumns sharing common labels (letters) are not significantly different from each other (p>0.05).
Mentions: In homozygous ala3 mutants, seed set in each silique was decreased to ∼59% that of wild-type (Figure 5). A high frequency of empty seed positions were observed within ala3 siliques, the majority of which were near the bottom of the silique (Figure 5a, c). This uneven seed distribution was reversed by manual fertilization of ala3 pistils with wild-type pollen (Figure S3), consistent with the potential that homozygous plants either shed less pollen or have defective pollen. However, an explanation based on a pollen fitness problem is favored by in-vitro growth (Figure 4) and in-vivo competition (Table 2) assays, both of which indicate a pollen defect.

Bottom Line: We also demonstrate that ala3 mutants have reduced fecundity resulting from a combination of decreased ovule production and pollen tube growth defects.In-vitro pollen tube growth assays showed that ala3 pollen germinated ∼2 h slower than wild-type and had approximately 2-fold reductions in both maximal growth rate and overall length.Together, these results support a model in which ALA3 functions to modify endomembranes in multiple cell types, enabling structural changes, or signaling functions that are critical in plants for normal development and adaptation to varied growth environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada, United States of America.

ABSTRACT
Members of the P4 subfamily of P-type ATPases are thought to help create asymmetry in lipid bilayers by flipping specific lipids between the leaflets of a membrane. This asymmetry is believed to be central to the formation of vesicles in the secretory and endocytic pathways. In Arabidopsis thaliana, a P4-ATPase associated with the trans-Golgi network (ALA3) was previously reported to be important for vegetative growth and reproductive success. Here we show that multiple phenotypes for ala3 knockouts are sensitive to growth conditions. For example, ala3 rosette size was observed to be dependent upon both temperature and soil, and varied between 40% and 80% that of wild-type under different conditions. We also demonstrate that ala3 mutants have reduced fecundity resulting from a combination of decreased ovule production and pollen tube growth defects. In-vitro pollen tube growth assays showed that ala3 pollen germinated ∼2 h slower than wild-type and had approximately 2-fold reductions in both maximal growth rate and overall length. In genetic crosses under conditions of hot days and cold nights, pollen fitness was reduced by at least 90-fold; from ∼18% transmission efficiency (unstressed) to less than 0.2% (stressed). Together, these results support a model in which ALA3 functions to modify endomembranes in multiple cell types, enabling structural changes, or signaling functions that are critical in plants for normal development and adaptation to varied growth environments.

Show MeSH
Related in: MedlinePlus