Membrane Lipid Remodelling of Meconopsis racemosa after Its Introduction into Lowlands from an Alpine Environment

Li W (2014) Membrane Lipid Remodelling of Meconopsis racemosa after Its Introduction into Lowlands from an Alpine Environment. PLoS ONE 9(9): e106614. doi:10.1371/journal.pone.0106614 Membrane Lipid Remodelling of Meconopsis racemosa after Its Introduction into Lowlands from an Alpine Environment Guowei Zheng 0 Bo Tian 0 Weiqi Li 0 Ing-Feng Chang, National Taiwan University, Taiwan 0 1 Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences , Kunming, Yunnan , People's Republic of China, 2 Key Laboratory of Tropical Plant Resource and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences , Kunming , People's Republic of China, 3 Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences , Kunming, Yunnan , People's Republic of China Membrane lipids, which determine the integrity and fluidity of membranes, are sensitive to environmental changes. The influence of stresses, such as cold and phosphorus deficiency, on lipid metabolism is well established. However, little is known about how plant lipid profiles change in response to environmental changes during introduction, especially when plants are transferred from extreme conditions to moderate ones. Using a lipidomics approach, we profiled the changes in glycerolipid molecules upon the introduction of the alpine ornamental species Meconopsis racemosa from the alpine region of Northwest Yunnan to the lowlands of Kunming, China. We found that the ratios of digalactosyldiacylglycerol/ monogalactosyldiacylglycerol (DGDG/MGDG) and phosphatidylcholine/phosphatidylethanolamine (PC/PE) remained unchanged. Introduction of M. racemosa from an alpine environment to a lowland environment results in two major effects. The first is a decline in the level of plastidic lipids, especially galactolipids. The second, which concerns a decrease of the double-bond index (DBI) and could make the membrane more gel-like, is a response to high temperatures. Changes in the lipidome after M. racemosa was introduced to a lowland environment were the reverse of those that occur when plants are exposed to phosphorus deficiency or cold stress. - Funding: The study was supported by grants from NSFC 30670474 & 30870571, West Light Foundation of the Chinese Academy of Sciences (CAS), Germplasm Bank of Wild Species, the CAS Innovation Program of Kunming Institute (540806321211) and the 100 Talents Program, CAS. The study was also supported by grants from (NSFC 31371661). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. Plant introduction and acclimatization, the products of which now account in large part for many of our foods and ornamental species, played a critical role in the emergence of civilisation [1]. During the process of introduction, plants are transferred from their native environments to artificial ones where resources are usually plentiful and the plants can avoid stresses, such as freezing, drought, nutrient deprivation, and infection with pathogens [1,2]. The major obstacle to successful introduction is whether plants can adapt to dramatic changes in their environment. For example, the introduction of alpine plants to a lowland environment for the purpose of preservation and sustainable use is very difficult, because few plants can overcome considerable changes in temperature, irradiation, water conditions, and even nutrition [35]. Most studies of plant adaptation to environmental changes have focused on the adaption to stresses in which environments shift from optimum to adeverse conditions [6,7]. The mechanisms that plants use to adapt to moderate environments after their transfer from extreme environments are not fully understood. Given that the responses of an organism to two opposite stimuli are often not simply the direct inverses of each other, understanding how plants adapt to the transfer from alpine to lowland conditions is an issue of biological significance and commercial importance. Plants can adapt to environmental changes by adjustments at the morphological, physiological, biochemical, and molecular levels [68]. Membranes are integral to the structure and function of all cells; maintenance of the integrity and fluidity of membranes is of fundamental importance if plants are to survive environmental changes [911]. Glycerolipids are the major constituents of membranes. Lipid remodeling, through adjustment of the composition, unsaturation (represented by the double-bond index, DBI) and the acyl chain lengths (ACL) of their constituent fatty acids, is one of the most important ways that plants use to maintain the function of membranes upon exposure to fluctuating environmental conditions. Plants tend to synthesise additional galactolipids to replace phospholipids under conditions of phosphate deficiency [1214], but to increase the proportion of phospholipids in response to low temperatures [15,16]. Membrane lipids, such as DGDG and phosphatidylcholine (PC), have relatively large polar head groups that tend to form membranes with the lamellar phase (La), which can enhance the stability of the membrane under various stresses. In contrast, monogalactosyldiacylglycerol (MGDG) and phosphatidylethanolamine (PE)which have relatively small head groupsshow a higher propensity for transition to the non-bilayer HII-type structures. The increased ratio of DGDG/MGDG and PC/PE could enhance the stability of the membrane under temperature and dehydration stresses [1720]. Changes of the DBI and ACL of membrane glycerolipids that enable the fluidity of membranes to be adjusted are other important responses of membranes to stress, especially that caused by temperature extremes. Low temperature results in a 31% increase in the degree of unsaturation of fatty acids [21]. In contrast, the degree of unsaturation of fatty acids in plants decreases following exposure to high temperatures. For example, the DBI of Arabidopsis plants grown at 36uC was 39% lower than that of plants grown at 17uC [22]. Alternatively, whereas longerchain fatty acids can make the membrane environment more gellike, shorter chains help to maintain the fluid state of membranes [23]. As such, in bacteria, it is common to see a decrease in the average length of fatty acyl chains as the growth temperature decreases [24]. In alpine-scree ecosystems of the Baima Snow Mountain in Northwest China, the daytime temperature exceeds 35uC, whereas the temperature at night can drop below freezing [5]; in addition, the level of available phosphorus is very low (1.3 ppm) [25]. Meconopsis racemosa, a member of the Papaveraceae, is a native of the alpine scree of the Baima Snow Mountain. It is a well-known hortic (...truncated)