A detailed analysis of the structure and function, along with evolutionary aspects, of the main plant cytosine-5 DNA methyltransferases (C5-MTases) is presented. The evolutionary relationships ...between the already known and four candidate plant C5-MTases identified in this work were investigated using the distance, maximum-parsimony, and maximum-likelihood approaches. The topologies of the trees were overall congruent: four monophyletic groups corresponding to the four plant C5-MTase families were clearly distinguished. In addition, sequence analyses of the plant C5-MTase target recognition domain sequences were performed and phylogenetic trees were reconstructed showing that there is good conservation
among but not
within the plant C5-MTase families. Furthermore, a conserved dipeptide that plays an important role in flipping the target base into the catalytic site of the C5-MTases was identified in all plant C5-MTases under study.
Jacques Arnould thanks Stephen Hawking for his warning, but then quickly moves on to contend: the present moment provides an opportunity for Homo sapiens on Earth to rediscover the virtue of ...discretion.
There is growing debate about whether we should attempt to message extraterrestrials (METI). Much of the debate has focused on the level of risk posed and in particular, the barn door argument (BDA), ...holds that aliens would already know about us and thus there is little harm that could come from messaging. In this article, I examine the basic logic of BDA by comparing it with Pascal's Wager. These are both intuitive appeals that try to sidestep the empirical debate, but on critical examination they are seen to fall prey to a number of similar problems.
A Belgian field strain (MR-VP) of Tetranychus urticae (Koch) (Acari: Tetranychidae) exhibits different levels of resistance to four frequently used METI (mitochondrial electron transport ...inhibitor)-acaricides, i.e. tebufenpyrad, fenpyroximate, pyridaben and fenazaquin. Resistance factors for these compounds were 184, 1547, 5971 and 35, respectively. A 23.5-fold increase in 7-ethoxy-4-trifluoromethylcoumarin O-deethylation activity suggested that metabolic resistance through elevated levels of cytochrome P450 dependent monooxygenase-activity is a possible resistance mechanism. However, synergism studies with different metabolic inhibitors revealed some contrasting resistance mechanisms between the METI-acaricides. Tebufenpyrad resistance could only be synergized after pre-treatment with the monooxygenase inhibitor piperonyl butoxide (PBO), whereas pyridaben resistance was strongly synergized both by PBO and the esterase inhibitor S,S,S-tributylphosphorotrithioate (DEF). Resistance levels to fenpyroximate could neither be suppressed by PBO nor by DEF. Although METI-acaricides are structurally related, these findings probably reflect a different role of esterases and mono-oxygenases in metabolic detoxification between these compounds. The overall lack of synergism by diethylmaleate (DEM) suggests that glutathione-S-transferases are not an important factor in resistance to METIs. Reciprocal crosses between susceptible females and resistant males showed no maternal effect, and resistance to METI-acaricides was inherited generally as a dominant trait. Backcrosses with F1 females revealed striking differences in the mode of inheritance. Although resistance to fenpyroximate and pyridaben was under monogenic control, resistance to tebufenpyrad was under control of more than one gene.
Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates ...spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise, and also have a large time-bandwidth product. Thus spread spectrum also provides an implicit coordination between transmitter and receiver by reducing the ambiguity as to the signal character. This strategy requires the receiver to guess the specific noise-like signal, and it is contended that this is feasible if an appropriate pseudorandom signal is generated algorithmically. For example, conceptually simple algorithms like the binary expansion of common irrational numbers like π are shown to be suitable. Due to its deliberately wider bandwidth, spread spectrum is more susceptible to dispersion and distortion in propagation through the interstellar medium, desirably reducing ambiguity in parameters like bandwidth and carrier frequency. This suggests a promising new direction in interstellar communication using spread spectrum modulation techniques.
► Spread spectrum modulation counters radio-frequency interference (RFI). ► A spread-spectrum signal should statistically resemble white noise. ► This observation aids transmitter–receiver coordination. ► White-noise-like signals can be generated by simple and universal algorithms. ► Spread spectrum is attractive for interstellar communication.
Insights from the robust field of risk communication and perception have to date been almost totally absent from the policy debate regarding the relative risks and merits of Active SETI or Messaging ...to Extraterrestrial Intelligence (METI). For many years, the practice (or proposed practice) of Active SETI has generated a vigorous and sometimes heated policy debate within the scientific community. There have also been some negative reactions in the media toward the activities of those engaged in Active SETI. Risk communication is a scientific approach to communication regarding situations involving potentially sensitive or controversial situations in which there may be high public concern and low public trust. The discipline has found wide acceptance and utility in fields such as public health, industrial regulation and environmental protection. Insights from the scientific field of risk communication (such as omission bias, loss aversion, the availability heuristic, probability neglect, and the general human preference for voluntary over involuntary risks) may help those who have participated in either side of the debate over Active SETI to better understand why the debate has taken on this posture. Principles of risk communication and risk perception may also help those engaged in Active SETI to communicate more effectively with other scientists, the public, with the media, and with policy makers regarding their activities and to better understand and respond to concerns expressed regarding the activity.
•Risk communication may be relevant to the policy debate regarding Active SETI.•Examples include omission bias and loss aversion.•Other examples include the availability heuristic and probability neglect.•General preference for voluntary over involuntary risks may also be relevant.
Astrotheology, not simply a theology of space sciences, is necessary because astrobiology effects a conceptual shift in how we ask the question "Why do we exist?" Here I suggest characterizing that ...shift in terms of the intra-action of living systems and habitable environments, which has serious implications for approaches to doctrinal theology. I consider this in terms of the imago Dei and what implications a transdisciplinary approach to astrotheology might in turn have for reframing SETI and METI endeavors as a quest for an Extraterrestrial imago Dei (SETiD or METiD).
There is currently a divide among astrobiologists on the question of whether to transmit intentional, directed messages into space. This debate raises several questions pertaining to space ethics, ...and it demands rigorous ethical analysis before active transmission occurs. Here we address ethical issues of responsibility, consensus, shared values, messaging content, communicative burden, and proscriptions on premature messaging. It is our hope that these deliberative contributions highlight the need for sustained analyses to precede the active messaging otherwise taking place. We maintain that these and other deliberations must occur in order that successful METI policies and protocols may be developed.
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