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Plant Physiol. 2020 Feb 12. pii: pp.01332.2019. doi: 10.1104/pp.19.01332. [Epub ahead of print]

The lipid flippases ALA4 and ALA5 play critical roles in cell expansion and plant growth.

Author information

1
University of Nevada, Reno CITY: Reno STATE: NV POSTAL_CODE: 89557 United States Of America [US].
2
University of Nevada, Reno CITY: Reno STATE: NV United States Of America [US].
3
University of Copenhagen CITY: Frederiksberg Denmark [DK].
4
University of Nebraska-Lincoln CITY: Lincoln STATE: NE POSTAL_CODE: 68588 United States Of America [US].
5
University of Nebraska-Lincoln CITY: Lincoln STATE: Nebraska United States Of America [US].
6
University of Copenhagen CITY: Frederiksberg C POSTAL_CODE: DK-1871 Denmark [DK].
7
The University of Nevada, Reno CITY: Reno STATE: Nevada POSTAL_CODE: 89557 United States Of America [US] jfharper@unr.edu.

Abstract

Aminophospholipid ATPases (ALAs) are lipid flippases involved in transporting specific lipids across membrane bilayers. Arabidopsis thaliana contains 12 ALAs in five phylogenetic clusters, including four in cluster 3 (ALA4, -5, -6, and -7). ALA4/5 and ALA6/7 are expressed primarily in vegetative tissues and pollen, respectively. Previously, a double knockout (KO) of ALA6/7 was shown to result in pollen fertility defects. Here we show that a double KO of ALA4/5 results in dwarfism, characterized by reduced growth in rosettes (6.5-fold), roots (4.3-fold), bolts (4.5-fold), and hypocotyls (2-fold). Reduced cell size was observed for multiple vegetative cell types, suggesting a role for ALA4/5 in cellular expansion. Members of the 3rd ALA cluster are at least partially interchangeable, as transgenes expressing ALA6 in vegetative tissues partially rescued ala4/5 mutant phenotypes, and expression of ALA4 transgenes in pollen fully rescued ala6/7 mutant fertility defects. ALA4-GFP displayed plasma membrane (PM) and endomembrane localization patterns when imaged in both guard cells and pollen. Lipid profiling revealed ala4/5 rosettes had perturbations in glycerolipid and sphingolipid content. Assays in yeast revealed that ALA5 can flip a variety of glycerolipids and the sphingolipid sphingomyelin across membranes. These results support a model whereby the flippase activity of ALA4/5 impacts the homeostasis of both glycerolipids and sphingolipids and is important for cellular expansion during vegetative growth.

PMID:
32051180
DOI:
10.1104/pp.19.01332
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