CONICET | Buscador de Institutos y Recursos Humanos

Mitochondria play important roles in the plant stress responses and the detoxification of thereactive oxygen species generated in the electron-transport chain. Expression of genes encodingstress-related proteins such as the mitochondrial small heat shock proteins (M-sHSP) isupregulated in response to different abiotic stresses. In Arabidopsis thaliana, three M-sHSPsparalogous genes were identified, although their function under physiological conditions remainselusive. The aim of this work is to uncover the in vivo function of all three M-sHSPs at the wholeplant level. To accomplish this goal, we analyzed the phenotype, proteomic, and metabolicprofiles of Arabidopsis knock-down lines of M-sHSPs (single, double, and triple knock-downlines) during normal plant growth. The triple knock-down plants showed the most prominentaltered phenotype at vegetative and reproductive stages without any externally applied stress.They displayed chlorotic leaves, growth arrest, and low seed production. Concomitantly, theyexhibited increased levels of sugars, proline, citric, malic and ascorbic acid, among othermetabolites. In contrast, single and double knock-down plants displayed a few changes in theirphenotype. A redundant function among the three M-sHSPs is indicated by the impairment invegetative and reproductive growth associated with the simultaneous loss of all three M-sHSPsgenes. The triple knock-down lines showed alteration of proteins mainly involved inphotosynthesis and antioxidant defense compared to the control plants. On the other hand, heatstress triggered a distinct cytosolic response pattern and the upregulation of other sHSP members,in the knock-down plants. Overall, depletion of all three M-sHSPs in Arabidopsis severelyimpacted fundamental metabolic processes, leading to alterations in the correct plant growth anddevelopment. These findings expand our knowledge about the contribution of organelle-specificM-sHSPs to healthy plant growth under non-stress condition.