New paper: Costs and benefits of evolved immune responses

Arun’s paper reporting the detailed costs and benefits of evolved immune priming is now published! In an exciting earlier study, we had found that flour beetles exposed to the pathogen Bacillus thuringiensis adapted rapidly via the evolution of either immune priming or pathogen resistance. The new work – led by Arun (now at Edinburgh University) and Imroze Khan (now at Ashoka University) – aimed to test whether these distinct evolved immune responses were costly for a suite of fitness-related traits, and whether these costs could explain how the responses evolved. While we find that immune priming does impose some fitness costs, increased basal resistance appears to be surprisingly cost-free. As a bonus, we found that the enhanced level of immune priming was also transferred across generations. The project involved a ton of painstaking work and careful analysis, and we are all quite proud of the paper. Give it a read!

New paper: Mistranslation increases phenotypic variation

Our collaborative work (with Shashi Thutupalli’s lab at NCBS) on tracking mistranslation-induced phenotypic variability is now published! Protein sequences often differ because of underlying differences in DNA sequence (i.e. genetic mutations). However, making mistakes while building the protein can also introduce differences in the protein sequence, although at a low frequency. Proteins altered in this manner cannot be inherited, but do they affect fitness linked traits? Laasya, Parth and Godwin (from Shashi’s lab) carried out experiments with wild type and error-prone cells, to test whether non-heritable protein sequence diversity can affect variability in important aspects of bacterial fitness, such as cell division times and survival under stresses like starvation. We found that high protein sequence diversity (via high mistranslation) indeed increases phenotypic variability at the single cell level, and impacts phenotype and fitness at the population level. For more, read the excellent NCBS news article by rotation student Nivedita Mukherjee here, or read the paper! Image credit: Nivedita Mukherjee

New paper: Evolutionary effects of non-genetic inheritance

Laasya’s single-author review on how non-genetic changes can contribute to evolution is now out in Current Genetics! Transfer of information in biology usually occurs from nucleic acids to protein, but not vice-versa (The Central Dogma). Any molecular alteration that does not change the DNA sequence (genotype) is generally short lived, and is thought to have a limited influence on evolution. In her article review, Laasya classifies and discusses the growing body of evidence for how temporary changes in protein and RNA can indirectly alter the genotype, and therefore influence long term evolution. In particular, she reviews evidence for the very few instances where a temporary non-DNA based change buys time for a longer lasting genetic change to occur. Most of the evidence comes from experiments using microbial systems; in particular E. coli and S. cerevisiae. Overall, if such feedback (protein to DNA) turns out to be repeatable and can be predicted, it would fundamentally change our understanding of the flow of information in biological systems. How much of the genetic change that we measure today was preceded by non-genetic changes? Do cells employ errors in translation and transcription as strategies to generate variation? Have cells evolved to rely more on genetic change in some environments and more on non-genetic changes in others? These are some of the open and exciting questions that emerge from the work reviewed in the review.

New paper: Microbiome of a generalist pest

Apart from humans, many organisms acquire beneficial bacterial partners from the food that they eat. But what about generalists, whose diet can vary every day? We asked whether the bacteria in the diet of the red flour beetle – a grain pest found across the world – impact the beetles’ fitness in different diets. For these beetles, flour is not only their diet, but also the environment in which they live. Aparna found that beetles derive many fitness benefits from microbes in wheat flour, which they have used for many generations. But microbes from the new diets are not important for beetle fitness. So, diet shifts can be problematic for generalists, because their bacterial partners may be missing. Read the paper here.

New paper: What do the colours of a female damselfly say?

Shantanu’s work on female colour variation in the widespread, tiny damselfly Agriocnemis pygmaea is now out! Females of this damselfly (seen at the campus pond) come in two colors: red and blue, as well as a bunch of intermediate forms. We wondered whether these colours represent allelic forms, or ontogenic (age-related) change. From laboratory studies and field observations at the pond, Shantanu found that the colour variation is ontogenic. Females start off red, and as they mature and develop eggs, they begin to look blue, resembling males. The colour change coincides with males becoming more interested in mating with them. Read the paper here, or the NCBS news article. Photograph: Shantanu Joshi.

New paper: Mistranslation can be good!

Our work on ‘useful’ mistakes in bacteria (E. coli) is finally out! Laasya and Parth found that making rebel proteins not encoded by our DNA can be a good thing. In cells that frequently make mistakes, the accumulated ‘junk’ proteins end up triggering a high alert situation. This allows the cells to better deal with various external assaults (like increased temperature, damage to DNA and so on). When everything is normal this isn’t a big deal; in fact the junk makes cells mildly sick.  Under stress though, the high alert and error prone cells get the upper hand, leaving behind the more accurate (but less prepared) regular cells. For more: read the paper, and an NCBS news article. And, enjoy this summary cartoon from Pranjal Gupta that was featured on the journal cover!