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Composition of Mitochondrial Complex I during the Critical Node of Seed Aging in Oryza sativa

Chen, Baoyin, Yin, Guangkun, Whelan, James, Zhang, Zesen, Xin, Xia, He, Juanjuan, Chen, Xiaoling, Zhang, Jinmei, Zhou, Yuanchang, Lu, Xinxiong
Journal of plant physiology 2019 v.236 pp. 7-14
NAD (coenzyme), Oryza sativa, biogenesis, enzymes, germination, mitochondria, oxidation, oxygen, oxygen consumption, quinones, rice, seedlings, seeds, viability
Previous studies have documented mitochondrial dysfunction during the critical node (CN) of rice (Oryza sativa) seed aging, including a decrease in the capacity of NADH dependent O2 consumption. This raises the hypothesis that changes in the activity of NADH:ubiquinone oxidoreductase (complex I) may play a role in seed aging. The composition and activity of complex I was investigated at the CN of aged rice seeds. Using BN-PAGE and SWATH-MS 52 complex I subunits were identified, nineteen for the first time to be experimentally detected in rice. The subunits of the matrix arm (N and Q modules) were reduced in abundance at the CN, in accordance with a reduction in the capacity to oxidise NADH, reducing substrate oxidation and increase ROS accumulation. In contrast, subunits in the P module increased in abundance that contains many mitochondrial encoded subunits. It is proposed that the changes in complex I abundance subunits may indicate a premature re-activation of mitochondrial biogenesis, as evidenced by the increase in mitochondrial encoded subunits. This premature activation of mitochondrial biogenesis may under-pin the decreased viability of aged seeds, as mitochondrial biogenesis is a crucial event in germination to drive growth before autotrophic growth of the seedling is established.