Research Of Subcellular Localization Of Antioxidant System In The Leaves Of Sabina Under Low Temperature Stress

Seedlings of Sabina przewalskii and Sabina chinensis were used to study the effects oflow temperature stress on lipid peroxidation products and antioxidant system in thesubcellular fractions of Sabina’s leaves. We explored the distribution differences insubcellular fractions and adopted the significant difference analysis and multiple comparisonsmethod to screen out subcellular antioxidant system that can effectively scavenging activeoxygen, which will be helpful to understand antifreeze adaptation mechanism of the evergreenwoody plants and provides theoretical basis for cloning of antioxidant substances gene insubcellular fractions. The results showed that:Under the different temperatures (20℃,4℃,0℃and－6℃) for the same processing time,MDA contents of Sabina increased dramatically in the initial stage of low temperature stress,while they decreased firstly and then increased in the later stage of low temperature stress.Under the same temperature for the different processing time (4d,8d,12d,16d and20d),MDA contents increased firstly and then decreased. In addition, compared with Sabinachinensis, MDA contents of Sabina przewalskii were lower, and the localization of MDAcontents in the leaves of two Sabina species was chloroplast＞mitochondria＞cytosol.Under the different temperatures (20℃,4℃,0℃and－6℃) for the same processing time,the antioxidant enzymes activities of Sabina species(SOD, POD, APX and GR) increasedfirstly and then decreased, and the highest value was obtained at4℃. However, CATactivities didn’t increase significantly, indicating that it was not sensitive to low temperaturestress, and it was not the main enzyme that scavenging active oxygen. Under the sametemperature for the different processing time (4d,8d,12d,16d and20d), the antioxidantenzymes activities (SOD, CAT, APX and GR) increased firstly and then decreased. However,POD activitives increased significantly in the later stage of low temperature stress, whichshowed POD activitives response was slower than the other antioxidant enzymes in the initialstage of low temperature stress, and it is not sensitive to low temperature stress in theantioxidant defense system. In addition, the higher activities of antioxidant enzymes (SOD,APX and GR) were found in Sabina przewalskii, but POD and CAT activities of Sabinaprzewalskii were lower than Sabina chinensis, and the localization of SOD and APX in theleaves of two Sabina species was chloroplast＞cytosol＞mitochondria, the localization ofCAT was mitochondria＞chloroplast＞cytosol, the localization of GR was mitochondria＞cytosol＞chloroplast, the localization of POD in Sabina przewalskii was cytosol＞chloroplast＞mitochondria, the localization of POD in Sabina chinensis was cytosol＞mitochondria＞chloroplast. Under the different temperatures (20℃,4℃,0℃and－6℃) for the same processing time,and under the same temperature for the different processing time (4d,8d,12d,16d and20d),antioxidants (ASA and GSH) contents increased firstly and then decreased, it accords with thestress rule of general plants, that is, antioxidants in subcellular fractions increase to scavengereactive oxygen with the decreasing of stress temperature, which shows that low temperaturestress has induced antioxidants. However, antioxidants decreases with the extension oftreatment time, and it’s clear that excess reactive oxygen is removed and the plants haveproduced adaptation to low temperature stress. In addition, the higher contents of ASA werefound in Sabina przewalskii, but GSH contenrs of Sabina przewalskii were lower than Sabinachinensis, and the localization of ASA in the leaves of two Sabina species was chloroplast＞cytosol＞mitochondria, the localization of GSH was mitochondria＞cytosol＞chloroplast, thelocalization of ASA-GSH cycle was chloroplast＞mitochondria＞cytosol.Generally speaking, under low temperature stress, the antioxidant substances increasedfirstly and then decreased in subcellular fraction of two Sabina species, which indicated thatthe subcellular fractions of plants had the ability of coordinating the antioxidant defense.Moreover, the subcellular distribution of lipid peroxidation products (MDA), antioxidantenzymes (SOD, APX and GR) and antioxidants (ASA and GSH) are significant different in theditterent subcellular fractions of Sabina, which showed that lipid peroxidation products andantioxidant substances were various in subcellular fractions and antioxidant substances in onlyone of certain organelles played a major role in scavenging active oxygen, and it providedtheoretical basis for cloning of antioxidant substances gene in subcellular fractions. But therewas interspecific difference among the antioxidant system of two Sabina species, the higheractivities and more contents of antioxidant substances (SOD, APX, GR and ASA) were foundin Sabina przewalskii, but MDA contents of Sabina przewalskii were lower than Sabinachinensis. It showed that Sabina przewalskii had a prevailing strategy in order to develop thetolerance to freezing than Sabina chinensis, which was consistent with their natural survivalenvironmental conditions.