Normal growth of Arabidopsis requires cytosolic invertase but not sucrose synthase
Normal growth of Arabidopsis requires cytosolic invertase but not sucrose synthase
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DOI：
10.1073/pnas.0900689106
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发表时间：
2009-08-04
影响因子：
11.1
通讯作者：
Smith, Alison M.
中科院分区：
文献类型：
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作者：
Barratt, D. H. Paul;Derbyshire, Paul;Smith, Alison M.
蔗糖中的碳进入植物的细胞代谢可以通过蔗糖合成酶（SUS）或蔗糖转化酶（INV）催化。这两种途径对细胞代谢和关键代谢物的产生有不同的影响，包括细胞壁前体UDPglucose。为了研究这两种蔗糖分解代谢途径在拟南芥（L.）中的重要性，我们培育了缺乏SUS 6种同工异构体中的4种的突变植株。这些突变体（sus1/sus2/sus3/sus4突变体）在除韧皮部外的所有细胞类型中都缺乏SUS活性。令人惊讶的是，突变植株在淀粉和糖含量、种子重量和脂质含量、纤维素含量和细胞壁结构方面都是正常的。缺少SUS其余2种异构体（sus5/sus6突变体）的植物，在韧皮部特异性表达，在筛元件的筛板中胼胝质数量减少。为了发现拟南芥的蔗糖分解代谢是否需要INVs而不是SUSs，我们进一步培育了缺乏两种密切相关的中性INV亚型的植株（cinv1/cinv2突变体），这两种亚型被预测为根中主要的细胞质形式。突变植物严重降低了生长速度。我们讨论了这些发现对我们理解植物非光合细胞的碳供应的意义。
The entry of carbon from sucrose into cellular metabolism in plants can potentially be catalyzed by either sucrose synthase (SUS) or invertase (INV). These 2 routes have different implications for cellular metabolism in general and for the production of key metabolites, including the cell-wall precursor UDPglucose. To examine the importance of these 2 routes of sucrose catabolism in Arabidopsis thaliana (L.), we generated mutant plants that lack 4 of the 6 isoforms of SUS. These mutants (sus1/sus2/sus3/sus4 mutants) lack SUS activity in all cell types except the phloem. Surprisingly, the mutant plants are normal with respect to starch and sugar content, seed weight and lipid content, cellulose content, and cell-wall structure. Plants lacking the remaining 2 isoforms of SUS (sus5/sus6 mutants), which are expressed specifically in the phloem, have reduced amounts of callose in the sieve plates of the sieve elements. To discover whether sucrose catabolism in Arabidopsis requires INVs rather than SUSs, we further generated plants deficient in 2 closely related isoforms of neutral INV predicted to be the main cytosolic forms in the root (cinv1/cinv2 mutants). The mutant plants have severely reduced growth rates. We discuss the implications of these findings for our understanding of carbon supply to the nonphotosynthetic cells of plants.