Turnover of Phosphatidic Acid through Distinct Signaling Pathways Affects Multiple Aspects of Pollen Tube Growth in Tobacco

Phosphatidic acid (PA) is an important intermediate in membrane lipid metabolism that acts as a key component of signaling networks, regulating the spatio-temporal dynamics of the endomembrane system and the cytoskeleton. Using tobacco pollen tubes as a model, we addressed the signaling effects of PA by probing the functions of three most relevant enzymes that regulate the production and degradation of PA, namely, phospholipases D (PLD), diacylglycerol kinases (DGKs), and lipid phosphate phosphatases (LPPs). Phylogenetic analysis indicated a highly dynamic evolution of all three lipid-modifying enzymes in land plants, with many clade-specific duplications or losses and massive diversification of the C2-PLD family. In silico transcriptomic survey revealed increased levels of expression of all three PA-regulatory genes in pollen development (particularly the DGKs). Using specific inhibitors we were able to distinguish the contributions of PLDs, DGKs, and LPPs into PA-regulated processes. Thus, suppressing PA production by inhibiting either PLD or DGK activity compromised membrane trafficking except early endocytosis, disrupted tip-localized deposition of cell wall material, especially pectins, and inhibited pollen tube growth. Conversely, suppressing PA degradation by inhibiting LPP activity using any of three different inhibitors significantly stimulated pollen tube growth, and similar effect was achieved by suppressing the expression of tobacco pollen LPP4 using antisense knock-down. Interestingly, inhibiting specifically DGK changed vacuolar dynamics and the morphology of pollen tubes, whereas inhibiting specifically PLD disrupted the actin cytoskeleton. Overall, our results demonstrate the critical importance of all three types of enzymes involved in PA production and degradation, with strikingly different roles of PA produced by the PLD and DGK pathways, in pollen tube growth

The abiotic environment of Heliamphora nutans (Sarraceniaceae): pedological and microclimatic observations on Roraima Tepui

The aim of this study was the study of the abiotic environment of the carnivorous pitcher plant Heliamphora nutans (Sarraceniaceae), including the microclimate and the geochemistry of the soil of the growing sites on Roraima Tepui and discuss their relevance within the recent model of carnivorous plant ecology. The soil was peaty and low in nutrients. The microclimate on the site was very balanced, with moderately cool temperatures, a constant high humidity and very low wind speed. Heliamphora was not exposed to any recognizable climatic stress. Previous macroclimatic measurements reflected the growth conditions of Heliamphora only incorrectly, since humidity decreased drastically with height. The apparent conflict with the common model of carnivorous plant ecology was caused by the dense surrounding vegetation. However, the leaf coverage of these non carnivorous plants was too low to cause significant insolation decrease for Heliamphora. Furthermore, the temperature regime of the pitcher fluid was more balanced than the temperature of the leaf. This may improve conditions for the growth of microorganisms in the pitcher fluid that contribute to the degredation of the plant's prey

Structural Sterols Are Involved in Both the Initiation and Tip Growth of Root Hairs in Arabidopsis thaliana[W]

Structural sterols are required for membrane integrity, cell growth, and plant development. This work shows that structural sterols are one of the early polarity markers during root hair formation and development in Arabidopsis. Local accumulation of structural sterols may regulate plasma membrane properties at the tip, vesicular trafficking, and progression of polarized tip growth of root hairs

Quantification of Protein Uptake by Endocytosis in Carnivorous Nepenthales

Carnivorous plants adsorb prey-derived nutrients partly by endocytosis. This study quantifies endocytosis in Drosophyllum lusitanicum, Drosera capensis, Drosera roseana, Dionaea muscipula and Nepenthes × ventrata. Traps were exposed to 1% fluorescent-labeled albumin (FITC-BSA), and uptake was quantified repeatedly for 64 h. Formation of vesicles started after ≤1 h in adhesive traps, but only after 16 h in species with temporary stomach (D. muscipula and N. × ventrata). In general, there are similarities in the observed species, especially in the beginning stages of endocytosis. Nonetheless, further intracellular processing of endocytotic vesicles seems to be widely different between species. Endocytotic vesicle size increased significantly over time in all species except in D. capensis. Fluorescence intensity of the endocytotic vesicles increased in all species except D. muscipula. After 64 h, estimates for FITC-BSA absorption per gland ranged from 5.9 ± 6.3 ng in D. roseana to 47.8 ± 44.3 ng in N. × ventrata, demonstrating that endocytosis substantially contributes to the adsorption of prey-derived nutrients