EVIDENCE FOR CHILLING-INDUCED OXIDATIVE STRESS IN MAIZE SEEDLINGS AND A REGULATORY ROLE FOR HYDROGEN-PEROXIDE
EVIDENCE FOR CHILLING-INDUCED OXIDATIVE STRESS IN MAIZE SEEDLINGS AND A REGULATORY ROLE FOR HYDROGEN-PEROXIDE
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DOI：
10.1105/tpc.6.1.65
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发表时间：
1994-01-01
期刊：
影响因子：
11.6
通讯作者：
STEWART, CR
中科院分区：
文献类型：
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作者：
PRASAD, TK;ANDERSON, MD;STEWART, CR
我们利用对低温敏感的玉米自交系的驯化现象，研究了萌发前玉米幼苗对低温的分子、生化和生理反应。3天大的幼苗暴露在4℃下7天，除非预先暴露在14℃下3天，否则不能在低温胁迫下存活。通过减法杂交和差异筛选，分离出三种低温驯化反应（CAR）基因，发现它们在驯化过程中存在差异表达。其中一种CAR基因被鉴定为猫，它编码线粒体过氧化氢酶3同工酶，这使我们假设寒冷会给幼苗施加氧化应激。在驯化和未驯化的幼苗冷却期间，过氧化氢水平升高。进一步的分子和生化分析表明，在驯化过程中，虽然超氧化物歧化酶活性没有受到影响，但cat3转录物水平以及过氧化氢酶和愈创木酚过氧化物酶的活性均有所升高。过氧化氢酶抑制剂氨三唑短期处理后的H2O2积累表明，过氧化氢酶3似乎是幼苗中重要的H2O2清除酶。对照3天大的幼苗，用H2O2或甲萘醌（一种产生超氧化物的化合物）预处理，在27℃下诱导抗寒性。这两种化学处理也增加了cat3转录本、过氧化氢酶3和愈创木酚过氧化物酶的活性。我们认为过氧化氢在低温下有双重作用。在驯化过程中，它的早期积累标志着过氧化氢酶3和愈创木酚过氧化物酶等抗氧化酶的产生；在4摄氏度时，在未适应环境的幼苗中，由于这些或其他抗氧化酶的水平较低，它在组织中积累到有害的水平。
We have taken advantage of an acclimation phenomenon in a chilling-sensitive maize inbred to investigate the molecular, biochemical, and physiological responses to chilling in preemergent maize seedlings. Three-day-old seedlings were exposed to 4 degrees C for 7 days and did not survive chilling stress unless they were preexposed to 14 degrees C for 3 days. cDNAs representing three chilling acclimation-responsive (CAR) genes were isolated by subtraction hybridization and differential screening and found to be differentially expressed during acclimation. Identification of one of these CAR genes as cats, which encodes the mitochondrial catalase3 isozyme, led us to hypothesize that chilling imposes oxidative stress in the seedlings. Hydrogen peroxide levels were elevated during both acclimation and chilling of nonacclimated seedlings. Further molecular and biochemical analyses indicated that whereas superoxide dismutase activity was not affected, the levels of cat3 transcripts and the activities of catalase3 and guaiacol peroxidase were elevated in mesocotyls during acclimation. Accumulation of H2O2 following a short treatment with aminotriazole, a catalase inhibitor, indicated that catalase3 seems to be an important H2O2-scavenging enzyme in the seedlings. Control 3-day-old seedlings pretreated with H2O2 or menadione, a superoxide-generating compound, at 27 degrees C induced chilling tolerance. Both of these chemical treatments also increased cat3 transcripts and catalase3 and guaiacol peroxidase activities. We suggest that peroxide has dual effects at low temperatures. During acclimation, its early accumulation signals the production of antioxidant enzymes such as catalase3 and guaiacol peroxidase; At 4 degrees C, in nonacclimated seedlings, it accumulates to damaging levels in the tissues due to low levels of these, and perhaps other, antioxidant enzymes.