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首页> 美国卫生研究院文献>other >Plastidic Phosphoglucose Isomerase Is an Important Determinant of Starch Accumulation in Mesophyll Cells Growth Photosynthetic Capacity and Biosynthesis of Plastidic Cytokinins in Arabidopsis
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Plastidic Phosphoglucose Isomerase Is an Important Determinant of Starch Accumulation in Mesophyll Cells Growth Photosynthetic Capacity and Biosynthesis of Plastidic Cytokinins in Arabidopsis

机译：质朴的磷酸葡萄糖异构酶是拟南芥中叶肉细胞淀粉积累生长光合能力和质朴细胞分裂素生物合成的重要决定因素。

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Phosphoglucose isomerase (PGI) catalyzes the reversible isomerization of glucose-6-phosphate and fructose-6-phosphate. It is involved in glycolysis and in the regeneration of glucose-6-P molecules in the oxidative pentose phosphate pathway (OPPP). In chloroplasts of illuminated mesophyll cells PGI also connects the Calvin-Benson cycle with the starch biosynthetic pathway. In this work we isolated pgi1-3, a mutant totally lacking pPGI activity as a consequence of aberrant intron splicing of the pPGI encoding gene, PGI1. Starch content in pgi1-3 source leaves was ca. 10-15% of that of wild type (WT) leaves, which was similar to that of leaves of pgi1-2, a T-DNA insertion pPGI null mutant. Starch deficiency of pgi1 leaves could be reverted by the introduction of a sex1 null mutation impeding β-amylolytic starch breakdown. Although previous studies showed that starch granules of pgi1-2 leaves are restricted to both bundle sheath cells adjacent to the mesophyll and stomata guard cells, microscopy analyses carried out in this work revealed the presence of starch granules in the chloroplasts of pgi1-2 and pgi1-3 mesophyll cells. RT-PCR analyses showed high expression levels of plastidic and extra-plastidic β-amylase encoding genes in pgi1 leaves, which was accompanied by increased β-amylase activity. Both pgi1-2 and pgi1-3 mutants displayed slow growth and reduced photosynthetic capacity phenotypes even under continuous light conditions. Metabolic analyses revealed that the adenylate energy charge and the NAD(P)H/NAD(P) ratios in pgi1 leaves were lower than those of WT leaves. These analyses also revealed that the content of plastidic 2-C-methyl-D-erythritol 4-phosphate (MEP)-pathway derived cytokinins (CKs) in pgi1 leaves were exceedingly lower than in WT leaves. Noteworthy, exogenous application of CKs largely reverted the low starch content phenotype of pgi1 leaves. The overall data show that pPGI is an important determinant of photosynthesis, energy status, growth and starch accumulation in mesophyll cells likely as a consequence of its involvement in the production of OPPP/glycolysis intermediates necessary for the synthesis of plastidic MEP-pathway derived hormones such as CKs.
机译：磷酸葡萄糖异构酶（PGI）催化6-磷酸葡萄糖和6-磷酸果糖的可逆异构化。它参与糖酵解和氧化戊糖磷酸途径（OPPP）中葡萄糖-6-P分子的再生。在受照叶肉细胞的叶绿体中，PGI还将Calvin-Benson循环与淀粉生物合成途径连接起来。在这项工作中，我们分离了pgi1-3，这是一种由于pPGI编码基因PGI1的异常内含子剪接而完全缺乏pPGI活性的突变体。 pgi1-3源叶中的淀粉含量为。野生型（WT）叶片的10-15％，类似于T-DNA插入pPGI空突变体pgi1-2的叶片。 pgi1叶片的淀粉缺乏症可以通过引入阻止β-淀粉水解淀粉分解的sex1无效突变来恢复。尽管先前的研究表明pgi1-2叶片的淀粉颗粒仅限于与叶肉和气孔保卫细胞相邻的束鞘细胞，但这项工作进行的显微镜分析显示pgi1-2和pgi1的叶绿体中存在淀粉颗粒-3叶肉细胞。 RT-PCR分析显示pgi1叶片中质体和质外β-淀粉酶编码基因的高表达水平，同时伴随着β-淀粉酶活性的增加。即使在连续光照条件下，pgi1-2和pgi1-3突变体都显示出缓慢的生长和降低的光合能力表型。代谢分析表明，pgi1叶片的腺苷酸能电荷和NAD（P）H / NAD（P）比均低于野生型叶片。这些分析还表明，pgi1叶片中质体2-C-甲基-D-赤藓糖醇4-磷酸酯（MEP）-通路衍生的细胞分裂素（CKs）的含量远低于WT叶片。值得注意的是，CKs的外源应用很大程度上恢复了pgi1叶片的低淀粉含量表型。总体数据表明，pPGI是决定叶肉细胞光合作用，能量状态，生长和淀粉积累的重要决定因素，可能是由于其参与了质体MEP途径衍生激素的合成所必需的OPPP /糖酵解中间体的生产作为CK。

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