Assessing the latitudinal gradient in herbivory

Plant–herbivore interactions occur in all ecosystems and provide a major avenue for energy flow to higher trophic levels. A long‐standing hypothesis to explain the latitudinal gradient in species diversity proposes that the relatively stable and frost‐free climate of the tropics should lead to more intense biotic interactions in tropical compared with temperate environments, giving rise to a greater diversity of plants and herbivores. Herbivory rates have been compared across latitudes to test this biotic interactions hypothesis, with herbivory typically being measured from observable leaf damage. However, we argue that a measure of percentage leaf damage alone does not straightforwardly reflect the cost of herbivory to the plant, and on its own does not constitute an appropriate test of the biotic interactions hypothesis. For a given amount of herbivory, the impact of herbivory is dependent upon many factors, such as the construction cost of the leaf, the growth and replacement rates and leaf life span. We investigate the latitudinal gradient in herbivory by analysing a large dataset of herbivory rates for 452 tree species and separating the species into those with short and long leaf life spans. We show that annual herbivory rates tend to be greater at lower latitudes for evergreen species (which have long‐lived leaves), but no trend in herbivory rate with latitude was found for species with short leaf life spans. Phylogenetic least squares regression assuming Ornstein‐Uhlenbeck processes also showed a negative effect of latitude on herbivory rate for evergreen trees, but we caution that viewing herbivory as a species trait is problematic. An integrative approach that incorporates leaf life span, as well as the costs of investment in growth and potential costs of losing leaf tissue, is needed to further our understanding of the ecological and evolutionary dynamics of herbivory.     

Quantitative analysis of dynamic protein-protein interactions in planta by a floated-leaf luciferase complementation imaging (FLuCI) assay using binary Gateway vectors

Dynamic protein-protein interactions are essential in all cellular and developmental processes. Protein-fragment complementation assays allow such protein-protein interactions to be investigated in vivo. In contrast to other protein-fragment complementation assays, the split-luciferase (split-LUC) complementation approach facilitates dynamic and quantitative in vivo analysis of protein interactions, as the restoration of luciferase activity upon protein-protein interaction of investigated proteins is reversible. Here, we describe the development of a floated-leaf luciferase complementation imaging (FLuCI) assay that enables rapid and quantitative in vivo analyses of protein interactions in leaf discs floating on a luciferin infiltration solution after transient expression of split-LUC-labelled interacting proteins in Nicotiana benthamiana. We generated a set of eight Gateway-compatible split-LUC destination vectors, enabling fast, and almost fail-safe cloning of candidate proteins to the LUC termini in all possible constellations. We demonstrate their functionality by visualizing the well-established homodimerization of the 14-3-3 regulator proteins. Quantitative interaction analyses of the molybdenum co-factor biosynthesis proteins CNX6 and CNX7 show that the luciferase-based protein-fragment complementation assay allows direct real-time monitoring of absolute values of protein complex assembly. Furthermore, the split-LUC assay is established as valuable tool to investigate the dynamics of protein interactions by monitoring the disassembly of actin filaments in planta. The new Gateway-compatible split-LUC destination vector system, in combination with the FLuCI assay, provides a useful means to facilitate quantitative analyses of interactions between large numbers of proteins constituting interaction networks in plant cells.     

Comparison of the carbon-sequestering abilities of pineapple leaf residue chars produced by controlled combustion and by field burning

This study was undertaken to compare the chemical properties and yields of pineapple leaf residue (PLR) char produced by field burning (CF) with that produced by a partial combustion of air-dried PLR at 340 °C for 3 h in a furnace (CL). Higher total C, lignin content, and yield from CL as well as the presence of aromatic compounds in the Fourier Transform Infrared spectra of the char produced from CL suggest that the CL process was better in sequestering C than was the CF process. Although the C/N ratio of char produced from CL was low indicating a high N content of the char, the C in the char produced from CL was dominated by lignin suggesting that the decomposition of char produced from CL would be slow. To sequester C by char application, the PLR should be combusted in a controlled process rather than by burning in the field.     

Crystal structure and substrate-binding mode of cellulase 12A from Thermotoga maritima

Cellulases have been used in many applications to treat various carbohydrate-containing materials. Thermotoga maritima cellulase 12A (TmCel12A) belongs to the GH12 family of glycoside hydrolases. It is a β-1,4-endoglucanase that degrades cellulose molecules into smaller fragments, facilitating further utilization of the carbohydrate. Because of its hyperthermophilic nature, the enzyme is especially suitable for industrial applications. Here the crystal structure of TmCel12A was determined by using an active-site mutant E134C and its mercury-containing derivatives. It adopts a β-jellyroll protein fold typical of the GH12-family enzymes, with two curved β-sheets A and B and a central active-site cleft. Structural comparison with other GH12 enzymes shows significant differences, as found in two longer and highly twisted β-strands B8 and B9 and several loops. A unique Loop A3-B3 that contains Arg60 and Tyr61 stabilizes the substrate by hydrogen bonding and stacking, as observed in the complex crystals with cellotetraose and cellobiose. The high-resolution structures allow clear elucidation of the network of interactions between the enzyme and its substrate. The sugar residues bound to the enzyme appear to be more ordered in the -2 and -1 subsites than in the +1, +2 and -3 subsites. In the E134C crystals the bound -1 sugar at the cleavage site consistently show the α-anomeric configuration, implicating an intermediate-like structure.     

Discovery of 5-(arenethynyl) hetero-monocyclic derivatives as potent inhibitors of BCR-ABL including the T315I gatekeeper mutant

Ponatinib (AP24534) was previously identified as a pan-BCR-ABL inhibitor that potently inhibits the T315I gatekeeper mutant, and has advanced into clinical development for the treatment of refractory or resistant CML. In this study, we explored a novel series of five and six membered monocycles as alternate hinge-binding templates to replace the 6,5-fused imidazopyridazine core of ponatinib. Like ponatinib, these monocycles are tethered to pendant toluanilides via an ethynyl linker. Several compounds in this series displayed excellent in vitro potency against both native BCR-ABL and the T315I mutant. Notably, a subset of inhibitors exhibited desirable PK and were orally active in a mouse model of T315I-driven CML.     

中国石灰岩专性凤仙花叶表皮特征及其分类学意义

通过光学显微镜和扫描电镜技术对中国产的8种凤仙花科植物叶表皮微形态特征进行了实验研究,其中6种产于石灰岩地区,另外2种作为对照.结果表明,中国石灰岩地区的6种凤仙花的叶表皮微形态上、下表皮差异明显,上表皮细胞为不规则形和多边形,一般不具气孔器;下表皮细胞均为不规则形,均具气孔器,气孔器多为不等型.上、下表皮细胞形状、垂...     

光质对烟叶光合特性、类胡萝卜素和表面提取物含量的影响

以烤烟云烟87为材料,在烟株团棵期和打顶期用透光率相近的有色薄膜分别对其进行遮光处理直到采收结束,研究光质对烟叶光合特性、类胡萝卜素和表面提取物含量的影响.结果表明:烟叶生育前期各光质的整体光合性能依次为红光＞自然光＞白光＞蓝光＞黄光,后期蓝光的作用逐渐凸显.烤后烟叶β-胡萝卜素和叶黄素含量之间呈极显著正相关,且β-胡萝卜素含量明显高于叶黄素含量.团棵期增加红光,打顶期补充蓝光,有利于提高烤后烟叶β-胡萝卜素和叶黄素含量.光质对腺毛分泌物中的β-西柏三烯二醇影响最大,对降茄二酮影响最小.烷烃类蜡质成分中的三十一烷、三十三烷和异三十三烷含量受光质影响较大,异三十二烷和二十九烷含量受光质影响较小.相对于腺毛分泌物和烷烃类蜡质而言,光质对新植二烯影响较小.黄膜处理烤后烟叶的腺毛分泌物及其降解产物总量最高,光质对新植二烯和烷烃类蜡质含量的影响存在多种变化.红光和蓝光对烟叶表面提取物的影响效应主要表现在烟株生长前期,黄光和白光的影响效应主要体现在烟株生长后期.烟株生长前期增加红光比例,有利于增加烤后烟叶新植二烯和烷烃类蜡质成分积累;烟株生长后期补充黄光光质有助于提高烤后烟叶腺毛分泌物含量和表面提取物总量.