Respiration and Alternative Oxidase in Corn Seedling Tissues during Germination at Different Temperatures

Abstract

Respiration rates of Zea mays L. seedling tissues grown at 30 and 140C were measured at 250C at different stages of seedling growth. Accumulation of heat units was used to define the developmental stages to compare respiration between the two temperatures. At both temperatures, respiration rates of most tissues were highest at the youngest stages, then declined with age. Respiration rates of mesocotyl tissue were the most responsive to temperature, being nearly twofold higher when grown at 14 compared to 300C. Alternative pathway respiration increased concomitantly with respiration and was higher in mesocotyls grown in the cold. When seedlings were started at 30 then transferred to 140C, the increase in altemative pathway respiration due to cold was not observed unless the seedlings were transferred before 2 days of growth. Seedlings transferred to 140C after growth at 300C for 2 days had the same altemative oxidase capacity as seedlings grown at 300C. Seedlings grown at 140C for 10 to 12 days, then transferred to 300C, lost alternative pathway respiratory capacity over a period of 2 to 3 days. Western blots of mitochondrial proteins indicated that this loss of capacity was due to a loss of the alternative oxidase protein. Some in vitro characteristics of mitochondna were determined. The temperature optimum for measurement of alternative oxidase capacity was 15 to 200C. At 41°C, very little altemative oxidase was measured, i.e., the mitochondrial oxygen uptake was almost completely sensitive to cyanide. This inactivation at 410C was reversible. After incubation at 410C, the alternative oxidase capacity measured at 250C was the similar to when it was measured at that temperature directly. Isolated mitochondria lost alternative oxidase capacity at the same rate when incubated at 410C as they did when incubated at 250C. Increasing the supply of electrons to isolated mitochondria increased the degree of engagement of the alternative pathway, whereas lower temperature decreased the degree of engagement. Lower temperatures did not increase the degree of engagement of the pathway in intact tissues. We interpret these observations to indicate that the greater capacity of alternative oxidase in cold-grown seedlings is a consequence of development at these low temperatures which results in elevated respiration rates. Low temperature itself does not cause greater capacity or engagement of the alternative oxidase in mitochondria that have developed under warm temperatures. Our hypothesis would be that the low growth temperatures require the seedlings to have a higher respiration rate for some reason, e.g., to prevent the accumulation of a toxic metabolite, and that the alternative pathway functions in that respiration.

Characterization of two non-homoeologous nuclear genes encoding mitochondrial alternative oxidase in common wheat.

“…The rice AOX1a mRNA levels increase in plants grown under low temperature conditions (Ito et al, 1997). When maize and tobacco plants were placed under low temperature conditions, both the capacity of the alternative pathway and the amount of AOX proteins increased (Stewart et al, 1990;Vanlerberghe and McIntosh, 1992a). The cold-responsiveness of Waox1a and Waox1c was studied by Northern blot analysis of mRNAs extracted from M808 plants.…”

Lower Growth Temperature Increases Alternative Pathway Capacity and Alternative Oxidase Protein in Tobacco

“…This has been investigated in whole tissues and/ or isolated mitochondria from maize (7,29,30), wheat (20), potato (10), Brassica (27), soybean (16), cucumber (24) tago (28), and other species. Although it appears there is an increased capacity (or potential) for AP respiration in these tissues, the degree of engagement of this respiratory pathway at lower temperatures is not clear because of the inherent problems in using KCN and SHAM to measure engagement (22).…”

Expression Profiling of Reciprocal Maize Hybrids Divergent for Cold Germination and Desiccation Tolerance

“…Extensive efforts have been devoted to understanding the genetics and physiology of the cold germination (CG) and desiccation tolerance (DT) traits (Burris, 2000;Hoegemeyer and Gutormsen, 2000). Changes in various compositional (oligosaccharides, lipids, hormones, enzymes, free radicals, and metabolic intermediates) and organellar/suborganellar properties (mitochondria, oil and protein bodies, starch grains, membrane integrity, and structure of chromatin and proteins) in the seed and germinating seedlings of maize have been reported to be associated with CG (Yacoob and Filion, 1986;Janowiak and Markowski, 1987;Stewart et al, 1990aStewart et al, , 1990bSchell et al, 1991;Prasad, 1996Prasad, , 1997Santis et al, 1999) and DT (Leprince et al, 1993(Leprince et al, , 1994(Leprince et al, , 1995Bochicchio et al, 1994aBochicchio et al, , 1994bOishi and Bewley, 1990;Chen and Burris, 1991;Brenac et al, 1997;Obendorf, 1997;Perdomo and Burris, 1998;Wolkers et al, 1998).…”