Postgerminative growth and lipid catabolism in oilseeds lacking the glyoxylate cycle
Postgerminative growth and lipid catabolism in oilseeds lacking the glyoxylate cycle
复制标题
DOI：
10.1073/pnas.97.10.5669
复制
发表时间：
2000-05-09
影响因子：
11.1
通讯作者：
Graham, IA
中科院分区：
文献类型：
--
作者：
Eastmond, PJ;Germain, V;Graham, IA
乙醛循环被认为是油料植物萌发后生长和幼苗建立所必需的。我们已经鉴定出两个等位基因突变体ICL-1和ICL-2，它们由于缺乏关键酶异柠檬酸裂解酶而缺乏乙醛循环。这些突变体证明乙醛酸循环不是萌发所必需的。此外，光合作用可以弥补萌发后生长过程中乙醛循环的缺失，只有当光照强度或日长减少时，幼苗的建立才会受到影响。外源糖的供应可以克服这一生长缺陷。ICL突变体还表明，乙醛循环对于幼苗在接近自然生长的长期黑暗条件下的存活和恢复是重要的。令人惊讶的是，尽管突变幼苗不能催化醋酸盐净转化为碳水化合物，但它们能够分解储存脂肪。结果表明，在萌发的油籽中，脂肪可以作为呼吸的碳源，脂肪酸分解代谢的产物可以从过氧化酶体传递到线粒体，而不依赖乙醛循环。然而，脂肪分解和幼苗的建立需要额外的逆性碳源。这一来源可以由乙醛循环提供，如果没有乙醛循环，则通过外源蔗糖或光合作用提供。
The glyoxylate cycle is regarded as essential for postgerminative growth and seedling establishment in oilseed plants. We have identified two allelic Arabidopsis mutants, icl-1 and icl-2 which lack the glyoxylate cycle because of the absence of the key enzyme isocitrate lyase. These mutants demonstrate that the glyoxylate cycle is not essential for germination. Furthermore, photosynthesis can compensate for the absence of the glyoxylate cycle during postgerminative growth, and only when light intensity or day length is decreased does seedling establishment become compromised. The provision of exogenous sugars can overcome this growth deficiency. The icl mutants also demonstrate that the glyoxylate cycle is important for seedling survival and recovery after prolonged dark conditions that approximate growth in nature. Surprisingly, despite their inability to catalyze the net conversion of acetate to carbohydrate, mutant seedlings are able to break down storage lipids. Results suggest that lipids can be used as a source of carbon for respiration in germinating oilseeds and that products of fatty acid catabolism can pass from the peroxisome to the mitochondrion independently of the glyoxylate cycle. However, an additional anaplerotic source of carbon is required for lipid breakdown and seedling establishment. This source can be provided by the glyoxylate cycle or, in its absence, by exogenous sucrose or photosynthesis.