Patatin-Related Phospholipase pPLAIIIβ-Induced Changes in Lipid Metabolism Alter Cellulose Content and Cell Elongation in Arabidopsis    

Abstract

The release of fatty acids from membrane lipids has been implicated in various plant processes, and the patatin-related phospholipases (pPLAs) constitute a major enzyme family that catalyzes fatty acid release. The Arabidopsis thaliana pPLA family has 10 members that are classified into three groups. Group 3 pPLAIII has four members but lacks the canonical lipase/esterase consensus catalytic sequences, and their enzymatic activity and cellular functions have not been delineated. Here, we show that pPLAIIIb hydrolyzes phospholipids and galactolipids and additionally has acyl-CoA thioesterase activity. Alterations of pPLAIIIb result in changes in lipid levels and composition. pPLAIIIb-KO plants have longer leaves, petioles, hypocotyls, primary roots, and root hairs than wild-type plants, whereas pPLAIIIb-OE plants exhibit the opposite phenotype. In addition, pPLAIIIb-OE plants have significantly lower cellulose content and mechanical strength than wild-type plants. Root growth of pPLAIIIb-KO plants is less sensitive to treatment with free fatty acids, the enzymatic products of pPLAIIIb, than wild-type plants; root growth of pPLAIIIb-OE plants is more sensitive. These data suggest that alteration of pPLAIIIb expression and the resulting lipid changes alter cellulose content and cell elongation in Arabidopsis.

Metabolic Interactions between the Lands Cycle and the Kennedy Pathway of Glycerolipid Synthesis in Arabidopsis Developing Seeds

“…Indeed, we detected significant upregulations at the transcript levels of four PLAs through transcriptome profiling. Greater enzymatic preference of these PLAs toward the sn-2 position revealed by previous studies (Rietz et al, 2010;Li et al, 2011) clearly raised the prospect of increased 1-acyl-LPC production during PC deacylation in the mutant. Therefore, the accumulated LPC in lpcat1 lpcat2-2 could be derived from a combination of defective LPC reacylation and an accelerated PC deacylation by PLA.…”

“…Among the 27 PLA family members, transcripts of sPLA 2 -a and the three PAT- PLAs (PAT-PLA-IIb, PAT-PLA-IIIa, and PAT-PLA-IIId) were all significantly upregulated in the lpcat1 lpcat2-2 seeds (see Supplemental Data Sets 1 and 2 online). sPLA 2 -a has been shown to be specific for sn-2 position of PC hydrolysis (Lee et al, 2005), and in vitro studies on PAT-PLAs have also revealed their greater preference for the sn-2 than the sn-1 position in PC hydrolysis (Rietz et al, 2010;Li et al, 2011). The increased transcript levels of these genes suggest that increased sn-2 deacylation of PC contributed to the maintenance of PC content in lpcat1 lpcat2-2.…”

Role of Aminoalcoholphosphotransferases 1 and 2 in Phospholipid Homeostasis in Arabidopsis

“…RNA extraction and real-time PCR analysis of transcript levels were performed as described previously (Li et al, 2011). Total RNA was extracted from leaves or seeds using an RNeasy Mini Kit (Qiagen) or an adapted cetyltrimethylammonium bromide (CTAB) method, respectively.…”

“…For PC fatty acid composition analysis, total leaf lipids were separated on TLC, and then the PC spot was recovered and analyzed by transmethylation and gas chromatography (Li et al, 2011).…”

“…PE and PC spots were collected and counted with a Tri-Carb liquid scintillation counter (Perkin-Elmer). The radioactivity of PC and PE was normalized to the total fatty acids in the sample, which was obtained by transmethylation of the aliquot from the same sample and quantified on gas chromatography with fatty acid 17:0 as internal standard (Li et al, 2011).…”