Ueno Osamu, Wakayama Masataka
Plant Physiology Department, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
J Plant Res. 2004 Dec;117(6):433-41. doi: 10.1007/s10265-004-0175-1. Epub 2004 Oct 5.
The amphibious leafless sedge Eleocharis retroflexa ssp. chaetaria expresses C(4)-like biochemical characteristics in both the terrestrial and submerged forms. Culms of the terrestrial form have Kranz anatomy, whereas those of the submerged form have Kranz-like anatomy combined with anatomical features of aquatic plant leaves. We examined the immunolocalization of C(3) and C(4) enzymes in culms of the two forms. In both forms, phosphoenolpyruvate carboxylase; pyruvate, Pi dikinase; and NAD-malic enzyme were compartmentalized between the mesophyll (M) and Kranz cells, but their levels were somewhat reduced in the submerged form. In the terrestrial form, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) occurred mainly in the Kranz cells, and weakly in the M chloroplasts. In the submerged form, the rubisco occurred at higher levels in the M cells than in the terrestrial form. In both forms, the C(4) pattern of enzyme expression was clearer in the M cells adjacent to Kranz cells than in distant M cells. During the transition from terrestrial to submerged conditions, the enzyme expression pattern changed in submerged mature culms that had been formed in air before submergence, and matched that in culms newly developed underwater. It seems that effects of both environmental and developmental factors overlap in the C(4) pattern expression in this plant.
两栖无叶莎草Eleocharis retroflexa ssp. chaetaria在陆生和水生形态下均表现出类似C4的生化特征。陆生形态的茎具有花环结构，而水生形态的茎具有类似花环的结构并结合了水生植物叶片的解剖特征。我们研究了这两种形态茎中C3和C4酶的免疫定位。在两种形态中，磷酸烯醇式丙酮酸羧化酶、丙酮酸磷酸双激酶和NAD-苹果酸酶都在叶肉细胞（M）和花环细胞之间进行区室化分布，但在水生形态中的含量有所降低。在陆生形态中，1,5-二磷酸核酮糖羧化酶/加氧酶（rubisco）主要出现在花环细胞中，在叶肉叶绿体中含量较少。在水生形态中，rubisco在叶肉细胞中的含量高于陆生形态。在两种形态中，与花环细胞相邻的叶肉细胞中C4酶表达模式比远处的叶肉细胞更清晰。在从陆生条件转变为水生条件的过程中，在空气中形成后再被淹没的成熟水生茎中，酶表达模式发生了变化，并与在水下新发育的茎中的模式相匹配。在这种植物的C4模式表达中，环境和发育因素的影响似乎相互重叠。
