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.
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.
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.
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!
Bacteria are so small and so ubiquitous that it seems like they should be found everywhere. But recent work shows that much like animals and plants, most bacteria have discrete distributions. We asked: does host association shape bacterial distribution in nature? In Pratibha’s first paper from the lab, we describe how bacteria from the genus Methylobacterium are distributed across nearly 40 different rice landraces from Arunachal Pradesh and Manipur. Collaborating with the labs of Shivaprasad and Radhika at NCBS, we found that bacterial carbon-use phenotypes are largely shaped by the landrace they inhabit. Suprisingly, sugar availability on rice leaves does not correlate with the carbon-use phenotypes, leaving us with many new questions. For more, read the paper. Meanwhile, enjoy this lovely illustration by Pranjal Gupta!
Kruttika’s work testing the impact of butterfly caterpillar microbiomes on growth and survival is published! This was a major collaborative effort with Krushnamegh Kunte, and very new kind of work for our lab. The results were puzzling because unlike patterns from other insects, butterflies seem to be just fine without their bacteria. But in conjunction with Rittik and Ashwin’s recent results with dragonflies, it seems that we’ve uncovered one end of the spectrum of host-microbe interactions. The end that spells “meh!” rather than “I need you”. Here’s a cartoon summary of the work by Kruttika and Shreya. Also read a lay summary here; or read the paper for more details!
Rittik Deb and Ashwin Nair’s paper on the gut bacterial communities of dragonflies is out! We sampled several species of dragonflies from different locations in India, and found that gut bacterial communities varied across host species, location, and season. For some of the dragonflies, we were also able to analyse gut contents, and found that these “generalist predators” eat quite different meals that probably end up introducing distinct bacteria in their guts. So, unlike in most other insects, dragonfly gut bacterial communities seem to be transient and are neutrally assembled (rather than host-selected). Read the paper for more details. Meanwhile, enjoy this beautiful summary of the paper by Pranjal Gupta!