Is There an Upper Limit to Genome Size?

O.H. was supported by the Marie Skłodowska Curie Action Individual Fellowship program (CAPITULA, grant agreement 657918

Ginkgo biloba Responds to Herbivory by Activating Early Signaling and Direct Defenses

Background: Ginkgo biloba (Ginkgoaceae) is one of the most ancient living seed plants and is regarded as a living fossil. G. biloba has a broad spectrum of resistance or tolerance to many pathogens and herbivores because of the presence of toxic leaf compounds. Little is known about early and late events occurring in G. biloba upon herbivory. The aim of this study was to assess whether herbivory by the generalist Spodoptera littoralis was able to induce early signaling and direct defense in G. biloba by evaluating early and late responses. Methodology/Principal Findings: Early and late responses in mechanically wounded leaves and in leaves damaged by S. littoralis included plasma transmembrane potential (Vm) variations, time-course changes in both cytosolic calcium concentration ([Ca 2+]cyt) and H2O2 production, the regulation of genes correlated to terpenoid and flavonoid biosynthesis, the induction of direct defense compounds, and the release of volatile organic compounds (VOCs). The results show that G. biloba responded to hebivory with a significant Vm depolarization which was associated to significant increases in both [Ca 2+] cyt and H 2O 2. Several defense genes were regulated by herbivory, including those coding for ROS scavenging enzymes and the synthesis of terpenoids and flavonoids. Metabolomic analyses revealed the herbivore-induced production of several flavonoids and VOCs. Surprisingly, no significant induction by herbivory was found for two of the most characteristic G. biloba classes of bioactive compounds; ginkgolides and bilobalides

Exogenously induced expression of ethylene biosynthesis, ethylene perception, phospholipase D, and Rboh-oxidase genes in broccoli seedlings

In higher plants, copper ions, hydrogen peroxide, and cycloheximide have been recognized as very effective inducers of the transcriptional activity of genes encoding the enzymes of the ethylene biosynthesis pathway. In this report, the transcriptional patterns of genes encoding the 1-aminocyclopropane-1-carboxylate synthases (ACSs), 1-aminocyclopropane-1-carboxylate oxidases (ACOs), ETR1, ETR2, and ERS1 ethylene receptors, phospholipase D (PLD)-α1, -α2, -γ1, and -δ, and respiratory burst oxidase homologue (Rboh)-NADPH oxidase-D and -F in response to these inducers in Brassica oleracea etiolated seedlings are shown. ACS1, ACO1, ETR2, PLD-γ1, and RbohD represent genes whose expression was considerably affected by all of the inducers used. The investigations were performed on the seedlings with (i) ethylene insensitivity and (ii) a reduced level of the PLD-derived phosphatidic acid (PA). The general conclusion is that the expression of ACS1, -3, -4, -5, -7, and -11, ACO1, ETR1, ERS1, and ETR2, PLD-γ 1, and RbohD and F genes is undoubtedly under the reciprocal cross-talk of the ethylene and PAPLD signalling routes; both signals affect it in concerted or opposite ways depending on the gene or the type of stimuli. The results of these studies on broccoli seedlings are in agreement with the hypothesis that PA may directly affect the ethylene signal transduction pathway via an inhibitory effect on CTR1 (constitutive triple response 1) activity

Digests: Salamanders’ slow slither into genomic gigantism

This article corresponds to Mohlhenrich, E. R., and R. L. Mueller. 2016. Genetic drift and mutational hazard in the evolution of salamander genomic gigantism. Evolution. DOI:10.1111/evo.13084

Reactive Oxygen Species in the Elongation Zone of Maize Leaves Are Necessary for Leaf Extension

The production and role of reactive oxygen species (ROS) in the expanding zone of maize (Zea mays) leaf blades were investigated. ROS release along the leaf blade was evaluated by embedding intact seedlings in 2′,7′-dichlorofluorescein-containing agar and examining the distribution of 2′,7′-dichlorofluorescein fluorescence along leaf 4, which was exposed by removing the outer leaves before embedding the seedling. Fluorescence was high in the expanding region, becoming practically non-detectable beyond 65 mm from the ligule, indicating high ROS production in the expansion zone. Segments obtained from the elongation zone of leaf 4 were used to assess the role of ROS in leaf elongation. The distribution of cerium perhydroxide deposits in electron micrographs indicated hydrogen peroxide (H(2)O(2)) presence in the apoplast. 2′,7′-Dichlorofluorescein fluorescence and apoplastic H(2)O(2) accumulation were inhibited with diphenyleneiodonium (DPI), which also inhibited O(⋅)(2)(−) generation, suggesting a flavin-containing enzyme activity such as NADPH oxidase was involved in ROS production. Segments from the elongation zone incubated in water grew 8% in 2 h. KI treatments, which scavenged H(2)O(2) but did not inhibit O(⋅)(2)(−) production, did not modify growth. DPI significantly inhibited segment elongation, and the addition of H(2)O(2) (50 or 500 μm) to the incubation medium partially reverted the inhibition caused by DPI. These results indicate that a certain concentration of H(2)O(2) is necessary for leaf elongation, but it could not be distinguished whether H(2)O(2), or other ROS, are the actual active agents