Auxin and Stringolactone Interaction in Extreme Phosphate Conditions

Abstract

Hormonal crosstalk between auxin and strigolactones regulates plant development and can fine-tune the root system. The extreme conditions of phosphate deficiency and excess caused drastic changes in the root architecture of Medicago truncatula LAX3 transgenic and wild type (WT) plants. M. truncatula overexpressed lines (MtLAX3-OE) were characterized by high plasticity of surviving phosphorus starvation, due to the significant increase in lateral root number (LRN) and the relative expression level of MtLAX3, MtMAX2, and MtMAX3 genes. The application of 7-days treatment with synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) led to dramatic stimulation of the LRN in the transgenic and WT plants, where high inorganic phosphate (Pi) concentration 216in culture media together with the auxin could save the phenotype for the knockdown lines (MtLAX3-RNAi). Both transgenic lines and WT plants were characterized by high plasticity of surviving phosphorus starvation or excess, after exogenous application of 2,4-D, due to the significant increase in LRN and the relative expression level of MtLAX3 and MtMAX2 in roots. The results presented in the chapter strongly contributed to understanding the interaction between auxin and strigolactones, their function in plant growth and development. This obtained knowledge could be used to optimize the crop growth of legumes in eroded and poor phosphate soils. WT wild type Pi inorganic phosphate 2,4-D 2,4-dichlorophenoxyacetic acid LR lateral root LRN lateral root number MR main root RH root hair