Session 3A — Lectures by Fellows/Associates

VA Raghunathan, RRI, Bengaluru

Induction of aerial and belowground tubers in potato: A classic example of developmental plasticity and modulation of plant architecture. View Presentation

Plants, being sessile, exhibit diverse developmental plasticity and modulate their growth in response to various environmental conditions. Potato is an important food crop after cereals and serves as a significant portion of the world’s subsistence food supply. In last two decades, crucial molecular signals (Mobile RNAs, proteins etc.) have been identified that govern potato development (tuberization). Remarkably, overexpression of microRNA156 provided the first evidence for induction of profuse aerial tubers from axillary-nodes under short-day photoperiod. Similar phenotype was noticed for overexpression of epigenetic modifiers - StMSI1 or StE(z)2, and knockdown of StBMI1. This striking phenotype prompted us to investigate its mechanistic basis. We showed that polycomb group proteins control microRNA156, phytohormone metabolism/transport/signalling, and key tuberization genes through histone modifications and regulate this phenotype. Tuberization (stolon-to-tuber transition) appears to be a dynamic process, and plethora of small RNAs and their targets coordinate this, besides tuberization genes, phytohormones and environmental factors. Presence of histone marks on key tuberization genes is evident in stolons under short-day photoperiod. More than 1000 common genes are associated with aerial and belowground tuber development, indicative of a common gene-regulatory network. We demonstrate that photoperiods and epigenetic mechanisms play a crucial role in controlling this phenotype in potato.