Physiological and Molecular Responses for Metalloid Stress in Rice—A Comprehensive Overview

Rice (Oryza sativa L.) an agro-economically important crop and a staple food for more than 3 billion people worldwide. In the era of climate change, food security is a major concern. The rice cultivation and production system is capable of contributing significantly to curbing global food shortages. However, as an implication of climate change as well as environmental pollution, global rice cultivation has faced multifarious constrains and suffered enormous loss of productivity and yield. Loss of soil characteristics as a result of the repeated use of fertilizers and pesticides along with other associated factors has affected rice productivity considerably. Rice is usually cultivated in a water holding system, therefore, the incidence of accumulation of residual heavy metals and metalloids from diverse sources in the soil remains significantly high, which ultimately has negative impacts on its growth and yield. It has also been observed that rice cultivated in such soil results in significantly high accumulation of nonessential elements in their grains and straw, ultimately affecting human health at large. Our understanding of metalloid stress responses and tolerance is not completely known in rice. With the advent of several approaches mostly functional-based genomics platforms, novel possibilities to figure out the diverse mechanisms associated with metalloid stress responses and tolerance mechanisms have evolved. This review comprehensively summarizes the understanding of metalloid (As, Al, B, and Si) stress response and tolerance in rice by exploring responses at physiological, biochemical and molecular levels. Several critical factors and regulatory mechanisms have been successfully explored in rice, which are primarily associated with metalloid stress tolerance. Several genes and proteins known to be related with metalloid stress tolerance need further analysis and exploration in order to understand the cellular and functional behavior of rice during metalloid stress. Novel approaches and strategies are essential to find out possible ways to improve metalloid stress adaptability and tolerance in rice. The datasets obtained through such studies can be successfully explored in molecular breeding initiatives to improve metalloid stress tolerance in rice in future.