Understanding of mechanistic details of Mediator functioning in plants is impeded as the knowledge of subunit organization and structure is lacking. In this study, an interaction map of Arabidopsis Mediator complex was analyzed to understand the arrangement of the subunits in the core part of the complex. Combining this interaction map with homology-based modeling, probable structural topology of core part of the Arabidopsis Mediator complex was deduced. Though the overall topology of the complex was similar to that of yeast, several differences were observed. Many interactions discovered in this study are not yet reported in other systems. AtMed14 and AtMed17 emerged as the key component providing important scaffold for the whole complex. AtMed6 and AtMed10 were found to be important for linking head with middle and middle with tail, respectively. Some Mediator subunits were found to form homodimers and some were found to possess transactivation property. Subcellular localization suggested that many of the Mediator subunits might have functions beyond the process of transcription. Overall, this study reveals role of individual subunits in the organization of the core complex, which can be an important resource for understanding the molecular mechanism of functioning of Mediator complex and its subunits in plants.

Mediator, a multiprotein complex involved in transcription of class II genes, was first discovered in yeast and then characterized in many metazoans revealing a striking structural conservation of the complex. However, sequences of Mediator subunits are not well conserved raising a question on the functional conservation of these individual subunits. In this study, expression of Med15 of Arabidopsis (AtMed15) in gal11∆ yeast could not complement the function of ScGal11 in galactose metabolism and resistance against cycloheximide. Surprisingly, AtMed15 changed the morphology of the yeast cells. The cells adhered strongly on the surface of the agar media, and showed robust flocculation in the liquid media without affecting the growth. The AtMed15-induced adhesion and flocculation were observed in different carbon sources. Calcium-assisted cell wall-bound mannan-binding proteins were found to be involved in this flocculation, which was unaffected by wide fluctuation of pH or temperatures revealing its constitutive robust nature. Expression of few flocculation related Flo genes was up-regulated in these cells. Interestingly, there was significant increase in ethanol production by the yeast expressing AtMed15. Robust and constitutive flocculation and increased ethanol production by yeast cells harbouring AtMed15 indicate an opportunity of its important usage in biotechnology industries.

Human replication protein A (RPA) is a heterotrimeric ssDNA binding protein responsible for many aspects of cellular DNA metabolism. The binding to and dissociation of the four individual DNA binding domains (DBDs) from DNA result in configurational dynamics of the RPA-DNA complexes which are essential for replacement of RPA by downstream proteins in various cellular metabolic pathways. RPA plays several important functions at telomeres where it binds to and melts telomeric G-quadruplexes, non-canonical DNA structures formed at the G-rich telomeric ssDNA overhangs. Here, we combine single-molecule total internal reflection fluorescence microscopy (smTIRFM), mass photometry (MP) with biophysical and biochemical analyses, of a gain-of-function RPA mutant to demonstrate that heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) specifically remodels RPA bound to telomeric ssDNA by dampening the RPA configurational dynamics and forming a stable ternary complex. Uniquely among hnRNPA1 target RNAs, TERRA is capable of releasing hnRNPA1 from the RPA-telomeric DNA complex. We speculate that this telomere specific RPA-DNA-hnRNPA1 complex is an important structure in telomere protection.

Background: Natural farming (NF) is a farming system that uses environmentally friendly pest and disease management practices. In contrast to chemical farming, it avoids use of synthetic fertilizers, pesticides and fungicides and hence, offers an alternative way for the eco-friendly pest management for the sustainable crop production. French bean crop is ravaged by wide array of insect pests wherein, sucking insect-pests like aphids, leaf miner and pod borer causing considerable damage. To manage these pests, farmers are spraying both recommended and non-recommended synthetic chemical pesticides having adverse effects on environment and human beings. Methods: Field experiment was conducted to evaluate the pest management strategies against sucking insect-pests and pod borer infesting French bean over a period of three years from 2019-20 to 2021-22 at College of Horticulture, Sirsi, Uttar Kannada (Hill Zone of Karnataka) during summer season. Four pest management modules viz., farmers practice, organic farming, natural farming (NF) and recommended package of practices (RPP) were evaluated to manage the pests in an eco-friendly manner. The field experiment was laid out in a randomized block design with five replications comprising of four treatments. The standard protocol was followed for recording observations. Result: Among the different modules tested, farmers practice recorded lowest population of aphids, leaf miner and pod borer and was at par with recommended package of practices. Whereas, Organic farming and natural farming recorded moderate level of pest infestation and quite safe for maintaining the predators like Coccinellids, Chrysoperla carnea and spider population for natural predation. The cost of plant protection measures was also least in these modules which indicates the socially and economically acceptable farming practices which may be adopted for safer French bean production.