Biology subjects

Priyadarshini, N.

Publications and source records attributed to Priyadarshini, N..

3 recordsLinked to original sources

bioRxiv2024

Light and temperature-dependent developmental role of Auxin Binding Protein 1 (ABP1) in Arabidopsis thaliana

Auxin Binding Protein 1 (ABP1) is a small glycoprotein of about 22 kDa that has long been debated as the auxin receptor, and has been put into question for its unclear functions. Despite its conservancy during land plant evolution, its precise role in plant development is still elusive. Historically, it has been implicated in various rapid responses such as membrane polarization, calcium fluxes, TMK1-based cell-surface signalling, auxin canalization, etc. A relatively recent observation questioning the role of ABP1 in plant development led us to explore its probable functions if any. In the current study, we reinvestigated the plausible function of ABP1 using its CRISPR-based loss-of-function mutants, namely abp1-C1 and abp1-C2. Here we show that, ABP1 acts as a positive regulator for primary root elongation under red and secondary root elongation under blue light in seedlings at 22 {degrees}C. Under red light at 18 {degrees}C, it has a negative effect on hypocotyl growth inhibition. Furthermore, it is involved in flowering time control at 18 {degrees}C irrespective of the photoperiod. We show that the transcript levels of Phytochrome B (phyB) and GIGANTEA (GI) are altered in the mutants of ABP1 under red light and low temperature (18 {degrees}C) regimes. Further, ABP1 show a pronounced role in tolerance to dehydration induced due to low temperature (18 {degrees}C), which correlates with an increase in endogenous abscisic acid (ABA), salicylic acid (SA), and a decrease in jasmonic acid (JA) content in leaves. The functional roles of ABP1 under red light, low temperature and dehydration tolerance in Arabidopsis thaliana once again frames it to be an important regulator under adverse and varied conditions that the plant can experience, and thus opened up new avenues for further studies.

plant biology↗

bioRxiv2023

Downregulation of ribosomal RNA (rRNA) genes in human head and neck squamous cell carcinoma (HNSCC) cells is linked to rDNA promoter hypermethylation

Eukaryotes carry hundreds of ribosomal RNA (rRNA) genes as tandem arrays, which generate rRNA for protein synthesis. Humans carry ~ 400 rRNA gene copies, which are epigenetically regulated. Dysregulation of rRNA synthesis and ribosome biogenesis are characteristic features of cancers. Targeting aberrant rRNA expression for cancer therapy is being explored. Head and neck squamous cell carcinoma (HNSCC) is among the most prevalent cancers globally. Using quantitative PCR and bisulfite sequencing, we show that rRNA genes are downregulated and their promoters are hypermethylated in HNSCC cell lines. These finding may have relevance for prognosis and diagnosis for HNSCC.

cancer biology↗

bioRxiv2021

Green light perception paved the way for the diversification of GAF domain photoreceptors

Photoreceptors are proteins that sense incident light and then trigger downstream signaling events. Phytochromes are linear tetrapyrrole-binding photoreceptors present in plants, algae, fungi, and various bacteria. Most phytochromes respond to red and far-red light signals. Among the phytochrome superfamily, cyanobacteria-specific cyanobacteriochromes show much more diverse optical properties covering the entire visible region. Both phytochromes and cyanobacteriochromes share the GAF domain scaffold to cradle the chromophore as the light-sensing region. It is unknown what physiological demands drove the evolution of cyanobacteriochromes in cyanobacteria. Here we utilize ancestral sequence reconstruction and report that the resurrected ancestral cyanobacteriochrome proteins reversibly respond to green and red light signals. pH titration analyses indicate that the deprotonation of the bound phycocyanobilin chromophore enables the photoreceptor to perceive green light. The ancestral cyanobacteriochromes show modest thermal reversion to the green light-absorbing form, suggesting that they evolved to sense green-rich irradiance rather than red light, which is preferentially utilized for photosynthesis. In contrast to plants and green algae, many cyanobacteria can utilize green light for photosynthesis with their special light-harvesting complexes, phycobilisomes. The evolution of green/red sensing cyanobacteriochromes may therefore have allowed ancient cyanobacteria to acclimate to different light environments by rearranging the absorption capacity of the cyanobacterial antenna complex by chromatic acclimation. Significance StatementLight serves as a crucial environmental stimulus affecting the physiology of organisms across all kingdoms of life. Photoreceptors serve as important players of light responses, absorbing light and actuating biological processes. Among a plethora of photoreceptors, cyanobacteriochromes arguably have the wealthiest palette of color sensing, largely contributing to the success of cyanobacteria in various illuminated habitats. Our ancestral sequence reconstruction and the analysis of the resurrected ancestral proteins suggest that the very first cyanobacteriochrome most probably responded to the incident green-to-red light ratio, in contrast to modern red/far-red absorbing plant phytochromes. The deprotonation of the light-absorbing pigment for green light-sensing was a crucial molecular event for the invention of the new class of photoreceptors with their huge color tuning capacity.

biochemistry↗