CRISPR/Cas9-mediated disruption of the gamma carbonic anhydrase 2 gene leads to reduced mitochondrial complex I and growth alterations in tomato.

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conclusionDespite similar complex I reduction, γCA2 disruption in tomato, unlike in arabidopsis, triggers hormonal and developmental changes, challenging assumptions of conserved mitochondrial responses across plant species. NADH-ubiquinone oxidoreductase [complex I (CI)] is the main entry point of electrons to OXPHOS being essential for metabolism and redox balance. In most organisms, except animals and fungi, CI contains an additional domain composed of gamma carbonic anhydrase (γCA) subunits, termed the CA module. In Arabidopsis thaliana, this module includes AtɣCA1/3, AtɣCA2, and AtɣCAL1/2. AtɣCA2 is critical for CI biogenesis, yet its role in other species remains unclear. In tomato, the γCA family comprises SlɣCA1a, SlɣCA1b, SlɣCA2, and SlɣCAL. Here, we report the inactivation of the tomato SlɣCA2 using CRISPR/Cas9 technology. As in arabidopsis, SlɣCA2-KO tomato plants show comparable reduction in CI levels and activity and a similar decrease in oxygen consumption, yet display increased ATP levels in seeds. However, unlike arabidopsis, mutant tomato plants exhibit delayed seed germination and retarded growth and development. Our results further suggest that abscisic acid and gibberellin homeostasis is altered in SlɣCA2-KO plants. Together, these findings support a connection between mitochondrial respiration and hormonal regulation, by which plants adjust developmental processes to mitochondrial electron transport chain functionality, thereby preventing energy depletion during early growth stages.