Sonnewald U, Brauer M, von Schaewen A, Stitt M, Willmitzer L
Institut für Genbiologische Forschung Berlin, Germany.
Plant J. 1991 Jul;1(1):95-106. doi: 10.1111/j.1365-313x.1991.00095.x.
In higher plants sucrose plays a central roles with respect to both short-term storage and distribution of photoassimilates formed in the leaf. Sucrose is synthesized in the cytosol, transiently stored in the vacuole and exported via the apoplast. In order to elucidate the role of the different compartments with respect to sucrose metabolism, a yeast-derived invertase was directed into the cytosol and vacuole of transgenic tobacco plants. This was in addition to the targeting of yeast-derived invertase into the apoplast described previously. Vacuolar targeting was achieved by fusing an N-terminal portion (146 amino acids long) of the vacuolar protein patatin to the coding region of the mature invertase protein. Transgenic tobacco plants expressing the yeast-derived invertase in different subcellular compartments displayed dramatic phenotypic differences when compared to wild-type plants. All transgenic plants showed stunted growth accompanied by reduced root formation. Starch and soluble sugars accumulated in leaves indicating that the distribution of sucrose was impaired in all cases. Expression of cytosolic yeast invertase resulted in the accumulation of starch and soluble sugars in both very young (sink) and older (source) leaves. The leaves were curved, indicating a more rapid cell expansion or cell division at the upper side of the leaf. Light-green sectors with reduced photosynthetic activity were evenly distributed over the leaf surface. With the apoplastic and vacuolar invertase, the phenotypical changes induced only appear in older (source) leaves. The development of bleached and/or necrotic sectors was linked to the source state of a leaf. Bleaching followed the sink to source transition, starting at the rim of the leaf and moving to the base. The bleaching was paralleled by the inhibition of photosynthesis.
在高等植物中，蔗糖在叶片中形成的光合同化物的短期储存和分配方面起着核心作用。蔗糖在细胞质中合成，短暂储存于液泡中，并通过质外体输出。为了阐明不同区室在蔗糖代谢方面的作用，将一种酵母来源的转化酶导入转基因烟草植株的细胞质和液泡中。这是在之前描述的将酵母来源的转化酶靶向质外体之外的操作。通过将液泡蛋白马铃薯Patatin的N端部分（146个氨基酸长）与成熟转化酶蛋白的编码区融合，实现了向液泡的靶向。与野生型植株相比，在不同亚细胞区室中表达酵母来源转化酶的转基因烟草植株表现出显著的表型差异。所有转基因植株均生长受阻，同时根系形成减少。淀粉和可溶性糖在叶片中积累，表明在所有情况下蔗糖的分配均受到损害。细胞质酵母转化酶的表达导致淀粉和可溶性糖在非常幼嫩（库）叶和较老（源）叶中均积累。叶片弯曲，表明叶片上侧细胞扩张或细胞分裂更快。光合活性降低的浅绿色区域均匀分布在叶片表面。对于质外体和液泡转化酶，仅在较老（源）叶中诱导出表型变化。漂白和/或坏死区域的形成与叶片的源状态有关。漂白跟随库到源的转变，从叶边缘开始并向基部移动。漂白伴随着光合作用的抑制。
