An Essential Role of Mitochondrial α-Ketoglutarate Dehydrogenase E2 in the Basal Immune Response Against Bacterial Pathogens in Tomato.

Plants intensely modulate respiration when pathogens attack, but the function of mitochondrial respiration-related genes in plant-bacteria interaction is largely unclear. Here, the functions of α-ketoglutarate dehydrogenase (α) E2 subunit and alternative oxidase () were investigated in the interaction between tomato and the virulent bacterial pathogen pv. DC3000 (). inoculation suppressed the transcript abundance of α, but enhanced expression and salicylic acid (SA) accumulation. Gene silencing and transient overexpression approaches revealed that plant susceptibility to was significantly reduced by silencing α in tomato, but increased by overexpressing α in , whereas silencing or overexpressing of did not affect plant defense. Moreover, silencing octanoyltransferase (), engaged in the lipoylation of α-kGDH E2, significantly reduced disease susceptibility and hydrogen peroxide accumulation. Use of transgenic NahG tomato plants that cannot accumulate SA as well as the exogenous SA application experiment evidenced that α-kGDH E2 acts downstream of SA defense pathway. These results demonstrate tomato α plays a negative role in plant basal defense against in an AOX-independent pathway but was associated with lipoylation and SA defense pathways. The findings help to elucidate the mechanisms of mitochondria-involved plant basal immunity.