Mitochondrial perturbation negatively affects auxin signaling.

Mitochondria are crucial players in the signaling and metabolic homeostasis of the plant cell. The molecular components that orchestrate the underlying processes, however, are largely unknown. Using a chemical biology approach, we exploited the responsiveness of Arabidopsis UDP-glucosyltransferase-encoding UGT74E2 towards mitochondrial perturbation in order to look for novel mechanisms regulating mitochondria-to-nucleus communication. The most potent inducers of UGT74E2 shared a (2-furyl)acrylate (FAA) substructure that negatively affected mitochondrial function and was identified before as an auxin transcriptional inhibitor. Based on these premises, we demonstrated that perturbed mitochondria negatively affect the auxin signaling machinery. Moreover, chemical perturbation of polar auxin transport and auxin biosynthesis was sufficient to induce mitochondrial retrograde markers and their transcript abundance was constitutively elevated in the absence of the auxin transcriptional activators ARF7 and ARF19.

Separation and quantification of the cellular thiol pool of pea plants treated with heat, salt and atrazine.

A novel procedure for the separation of the cellular thiol pool according to the molecular weight and localization of compounds with sulphydryl groups is presented. This simple and rapid method allows the differentiation of thiols into three major fractions-low molecular weight (LMT, primarily glutathione and free cysteine), protein-bound (TPT) and pellet-bound (PBT, associated with cell walls and broken organelles). Moreover, determination of the ratio between surface (readily reactive) thiols (ATG) and those that are more or less buried in the protein structure (BTG) can be achieved. In intact pea leaves, the amounts of the total thiols (LMT+PBT+TPT) varies from 2.5 to 4.8 micromol/g of fresh material. The data for LMT, PBT and TPT were related to each other in the approximate ratio 1:2:7. Treatments of pea plants with high temperature, salinity and low amounts of atrazine affect these sulphydryl types differently. For a greater understanding of the applicability of this method to physiological research, the main mechanisms leading to alterations in the cellular thiol pool are discussed. Furthermore, it is suggested that the proportion of available to buried thiols (ATG/BTG) in proteins could be used as a convenient marker for stress impacts.