Analysis of Differential Root System Architecture (RSA) of Oryza sativa in Response to Phosphorous Deficiency Stress

Abstract

Phosphorous is an important nutrient which plays significant role in major metabolic pathways like membrane synthesis, glycolysis and respiration. Less availability of phosphorous is the main limitation for growth of plants in terrestrial ecosystem and to cope this nutrient deficiency plants increase lateral root growth which helps in the uptake of immobile nutrients like phosphorous by enhancing soil exploration and phosphorous acquisition. These morphological and physiological responses can be efficiently determined by analyzing Root System Architecture. We examined RSA and growth of root apical meristem of Oryza sativa grown in the phosphorous deficiency. Seedlings of seven different varieties of rice were grown under three different experimental conditions containing IX, O.SX and no phosphorous in the media. GiA, General Image Analysis of Roots, software was used to analyze the images of different varieties of Oryza sativa grown under controlled and stressed conditions. Traits such as specific root length, maximum number of roots, root diameter, network width and network area were examined. Results clearly indicated that no or very little concentration of phosphorous results in short length of primary root with increased density of lateral roots, which helps in the uptake of phosphorous. We concluded that concentration of the phosphorous present in the growth environment of 0. sativa does affect the architecture of its root system and increased density of lateral roots is a strategy of plants to survive in the stressful environment. Usually nutrient deficiencies can alter both ethylene synthesis and signaling so to explore the role of ethylene pathway in phosphorous deficiency conditions for plants we checked the expression of ERS 1 and AC02 genes from phosphorus deficient rice roots. Our gene and protein expression data showed the increased expression of target gene/proteins in the rice roots grown in phosphorus deficient conditions. Our data supports the role of ethylene signaling in regulation of phosphorus deficiency. Further research is required to study in depth analysis of ethylene signaling pathway and its interactions with other pathways to regulate the nutrient deficiencies.