Lipid utilization, gluconeogenesis, and seedling growth in Arabidopsis mutants lacking the glyoxylate cycle enzyme malate synthase
Lipid utilization, gluconeogenesis, and seedling growth in Arabidopsis mutants lacking the glyoxylate cycle enzyme malate synthase
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DOI：
10.1074/jbc.m407380200
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发表时间：
2004-10-08
影响因子：
4.8
通讯作者：
Smith, SM
中科院分区：
文献类型：
--
作者：
Cornah, JE;Germain, V;Smith, SM
本研究旨在研究拟南芥中glyoxylate cycle enzyme苹果酸合成酶（MLS）在脂质利用、糖异生和幼苗生长中的作用。我们假设在没有MLS的情况下，异柠檬酸裂解酶（ICL）产生的琥珀酸盐仍然可以进入三羧酸循环，而乙醛酸盐可以通过光呼吸途径的酶转化为糖。为了验证这一假设，我们分离了敲除的mls突变体，并研究了它们与野生型和icl突变体幼苗的生长和代谢。与icl幼苗相反，icl幼苗生长缓慢，不能将脂质转化为糖(Eastmond， P. J., Germain， V., Lange， P. R., Bryce， J. H., Smith， S. M. & Graham， I. A. (2000) Proc. Natl。学会科学。美国农业部（u.s.a . 97, 5669, 5674）， mls幼苗生长更快，使用脂质更快，并且能够更好地建立成植株。转录组学和代谢组学分析表明，icl幼苗表现出许多碳水化合物饥饿的特征，而mls幼苗与野生型差异相对较小。在光照条件下，mls幼苗比icl幼苗产生更多的糖，当饲喂[C-14]醋酸盐时，C-14标记的糖是icl幼苗的三倍，是野生型幼苗的一半以上。mls幼苗也比icl或野生型幼苗积累了更多的甘氨酸和丝氨酸，这与乙醛酸转移到这些光呼吸途径的中间产物相一致。我们得出结论，在细菌和真菌中，MLS对醋酸或脂肪酸的糖异生是必需的，而在拟南芥幼苗中，MLS对脂质利用和糖异生是部分不必要的。
The aim of this research was to test the role of the glyoxylate cycle enzyme malate synthase (MLS) in lipid utilization, gluconeogenesis, and seedling growth in Arabidopsis. We hypothesized that in the absence of MLS, succinate produced by isocitrate lyase (ICL) could still feed into the tricarboxylic acid cycle, whereas glyoxylate could be converted to sugars using enzymes of the photorespiratory pathway. To test this hypothesis we isolated knock-out mls mutants and studied their growth and metabolism in comparison to wild type and icl mutant seedlings. In contrast to icl seedlings, which grow slowly and are unable to convert lipid into sugars (Eastmond, P. J., Germain, V., Lange, P. R., Bryce, J. H., Smith, S. M. & Graham, I. A. ( 2000) Proc. Natl. Acad. Sci. U. S. A. 97, 5669 5674), mls seedlings grow faster, use their lipid more rapidly, and are better able to establish as plantlets. Transcriptome and metabolome analyses show that icl seedlings exhibit many features characteristic of carbohydrate starvation, whereas mls seedlings differ relatively little from wild type. In the light mls seedlings generate more sugars than icl seedlings, and when fed with [C-14] acetate, C-14-labeling of sugars is three times greater than in icl seedlings and more than half that in wild type seedlings. The mls seedlings also accumulate more glycine and serine than icl or wild type seedlings, consistent with a diversion of glyoxylate into these intermediates of the photorespiratory pathway. We conclude that, in contrast to bacteria and fungi in which MLS is essential for gluconeogenesis from acetate or fatty acids, MLS is partially dispensable for lipid utilization and gluconeogenesis in Arabidopsis seedlings.