Chloroplast phosphatases LPPγ and LPPε1 facilitate conversion of extraplastidic phospholipids to galactolipids.

Galactolipids comprise the majority of chloroplast membranes in plants, and their biosynthesis requires dephosphorylation of phosphatidic acid at the chloroplast envelope membranes. In Arabidopsis (Arabidopsis thaliana), the lipid phosphate phosphatases LPPγ, LPPε1, and LPPε2 have been previously implicated in chloroplast lipid assembly, with LPPγ being essential, as null mutants were reported to exhibit embryo lethality. Here, we show that lppγ mutants are in fact viable and that LPPγ, LPPε1, and LPPε2 do not appear to have central roles in the plastid pathway of membrane lipid biosynthesis. Redundant LPPγ and LPPε1 activity at the outer envelope membrane is important for plant development, and the respective lppγ lppε1 double mutant exhibits reduced flux through the ER pathway of galactolipid synthesis. While LPPε2 is imported and associated with interior chloroplast membranes, its role remains elusive and does not include basal nor phosphate limitation-induced biosynthesis of glycolipids. The specific physiological roles of LPPγ, LPPε1, and LPPε2 are yet to be uncovered, as does the identity of the phosphatidic acid phosphatase required for plastid galactolipid biosynthesis.

Arabidopsis ACYL CARRIER PROTEIN4 and RHOMBOID LIKE10 act independently in chloroplast phosphatidate synthesis.

ACYL CARRIER PROTEIN4 (ACP4) is the most abundant ACP isoform in Arabidopsis (Arabidopsis thaliana) leaves and acts as a scaffold for de novo fatty acid biosynthesis and as a substrate for acyl-ACP-utilizing enzymes. Recently, ACP4 was found to interact with a protein-designated plastid RHOMBOID LIKE10 (RBL10) that affects chloroplast monogalactosyldiacylglycerol (MGDG) biosynthesis, but the cellular function of this interaction remains to be explored. Here, we generated and characterized acp4 rbl10 double mutants to explore whether ACP4 and RBL10 directly interact in influencing chloroplast lipid metabolism. Alterations in the content and molecular species of chloroplast lipids such as MGDG and phosphatidylglycerol were observed in the acp4 and rbl10 mutants, which are likely associated with the changes in the size and profiles of diacylglycerol (DAG), phosphatidic acid (PA), and acyl-ACP precursor pools. ACP4 contributed to the size and profile of the acyl-ACP pool and interacted with acyl-ACP-utilizing enzymes, as expected for its role in fatty acid biosynthesis and chloroplast lipid assembly. RBL10 appeared to be involved in the conversion of PA to DAG precursors for MGDG biosynthesis as evidenced by the increased 34:x PA and decreased 34:x DAG in the rbl10 mutant and the slow turnover of radiolabeled PA in isolated chloroplasts fed with [14C] acetate. Interestingly, the impaired PA turnover in rbl10 was partially reversed in the acp4 rbl10 double mutant. Collectively, this study shows that ACP4 and RBL10 affect chloroplast lipid biosynthesis by modulating substrate precursor pools and appear to act independently.

Connecting research and teaching introductory cell and molecular biology using an Arabidopsis mutant screen.

A complex research project was translated into a Course-based Undergraduate Research Experience (CURE), which was implemented in sections of an introductory Cell and Molecular Biology laboratory course. The research laboratory generated an engineered plant line producing a growth-inhibiting, lipid-derived plant hormone and mutagenized this line. Students in the CURE cultured the mutagenized plant population and selected and characterized suppressor mutants. They learned to observe phenotypes related to the biosynthesis and perception of the plant hormone and explored the genetic and biochemical basis of these phenotypes. As the students studied the relevant genetic, molecular and biochemical concepts during this CURE, they were able to translate this knowledge into practice and develop scientific arguments. This CURE was a successful collaboration between the teaching lab and the research lab. It benefited both parties as the students had a real-life, deep learning experience in scientific methodology, while the research lab gathered data and materials for further studies.

The Role of Chloroplast Membrane Lipid Metabolism in Plant Environmental Responses.

Plants are nonmotile life forms that are constantly exposed to changing environmental conditions during the course of their life cycle. Fluctuations in environmental conditions can be drastic during both day-night and seasonal cycles, as well as in the long term as the climate changes. Plants are naturally adapted to face these environmental challenges, and it has become increasingly apparent that membranes and their lipid composition are an important component of this adaptive response. Plants can remodel their membranes to change the abundance of different lipid classes, and they can release fatty acids that give rise to signaling compounds in response to environmental cues. Chloroplasts harbor the photosynthetic apparatus of plants embedded into one of the most extensive membrane systems found in nature. In part one of this review, we focus on changes in chloroplast membrane lipid class composition in response to environmental changes, and in part two, we will detail chloroplast lipid-derived signals.

Complementary and Alternative Medicine Use Among US Adults With Headache or Migraine: Results from the 2012 National Health Interview Survey.

BACKGROUND: Given the safety concerns regarding pharmacological agents, and the considerable impact of headache and migraine on the sufferer's quality of life, many people seek other treatment options beyond conventional medication and care to address their symptoms; this includes complementary and alternative medicine (CAM). Some CAM interventions have shown promising results in clinical trials of headache and migraine management. Nonetheless, there has been little research exploring the reasons for using CAM, and the types of CAM used, among this population. OBJECTIVE: The study aimed to answer the following questions: (1) Which CAM modalities are used most frequently among migraine/headache sufferers? and (2) What are the self-reported reasons for CAM use among migraine/headache sufferers? METHODS: This secondary analysis of data from the 2012 U.S. NHIS (a national cross-sectional survey) examined the use of CAM among migraine/headache sufferers, including the main reasons related to CAM use. Data were weighted and analyzed using STATA 14.0. RESULTS: The sample of 34,525 adults included 6558 (18.7%) headache/migraine sufferers. Of the headache/migraine sufferers, a substantial proportion (37.6%, n = 2427) used CAM for various conditions; however, CAM use specifically for headache/migraine was much less prevalent (3.3%, n = 216). Of those who used CAM for headache/migraine, about half used CAM in conjunction with prescription (47.8%, n = 100) or over-the-counter medication (55.1%, n = 113). As severity of headache/migraine increased so did the likelihood of using CAM (severe migraine odds ratio [OR] = 2.32; 95% confidence interval [CI]: 1.41, 3.82; both recurring headache/severe migraine OR = 3.36; 95% CI: 2.08, 5.43; when compared to those with recurring headache only). The most frequently used CAM modality among all headache/migraine sufferers (N = 6558) was manipulative therapy (22.0%, n = 1317), herbal supplementation (21.7%, n = 1389) and mind-body therapy (17.9%, n = 1100). The top 3 reasons for using CAM for headache were general wellness (28.7%, n = 60/209), improving overall health (26.8%, n = 56/209), and reducing stress (16.7%, n = 35/209). CONCLUSIONS: Although CAM is used by many sufferers of headache/migraine, the use of CAM specifically for the treatment of headache/migraine is relatively low in the United States. The study also assesses the key differences of CAM use among headache/migraine sufferers in NHIS 2012 compared with those in NHIS 2007, and identifies shortfalls in the evidence-base of several CAM modalities used by U.S. adults for headache/migraine. This information may assist health providers and consumers in making informed decisions about the safest and most appropriate approach to managing headache/migraine.

A conserved rubredoxin is necessary for photosystem II accumulation in diverse oxygenic photoautotrophs.

In oxygenic photosynthesis, two photosystems work in tandem to harvest light energy and generate NADPH and ATP. Photosystem II (PSII), the protein-pigment complex that uses light energy to catalyze the splitting of water, is assembled from its component parts in a tightly regulated process that requires a number of assembly factors. The 2pac mutant of the unicellular green alga Chlamydomonas reinhardtii was isolated and found to have no detectable PSII activity, whereas other components of the photosynthetic electron transport chain, including photosystem I, were still functional. PSII activity was fully restored by complementation with the RBD1 gene, which encodes a small iron-sulfur protein known as a rubredoxin. Phylogenetic evidence supports the hypothesis that this rubredoxin and its orthologs are unique to oxygenic phototrophs and distinct from rubredoxins in Archaea and bacteria (excluding cyanobacteria). Knockouts of the rubredoxin orthologs in the cyanobacterium Synechocystis sp. PCC 6803 and the plant Arabidopsis thaliana were also found to be specifically affected in PSII accumulation. Taken together, our data suggest that this rubredoxin is necessary for normal PSII activity in a diverse set of organisms that perform oxygenic photosynthesis.