Effect of CAX1a TILLING mutations and calcium concentration on some primary metabolism processes in Brassica rapa plants.

Cation/H+ exchanger transporters (CAXs) are crucial in Ca2+ homeostasis and in the generation of Ca2+ profiles involved in signalling processes. Given the crucial role of CAX1 in Ca2+ homeostasis, CAX1 modifications could have effects on plant metabolism. Three Brassica rapa mutants for CAX1 were obtained through TILLING. The aim of this work is to assess the effect of the different mutations and different Ca2+ doses on plant metabolism. For this, the mutants and the parental line were grown under low, control and high Ca2+ doses and parameters related to nitrogen (N) and tricarboxylic acid (TCA) metabolisms, and amino acid (AAs) and phytohormone profiles were measured. The results show that BraA.cax1a mutations affect metabolism especially under high Ca2+ dose. Thus, BraA.cax1a-7 inhibited some N metabolism enzymes and activated photorespiration activity. On the opposite side, BraA.cax1a-12 mutation provides a better tolerance to high Ca2+ dose. This tolerance could be provided by an improved N and TCA metabolisms enzymes, and a higher glutamate, malate, indole-3-acetic acid and abscisic acid concentrations. Therefore, BraA.cax1a-12 mutation could be used for B. rapa improving; the metabolomics changes observed in this mutant could be responsible for a better tolerance to high Ca2+.