钙离子在水霉(Saprolegnia ferax)菌丝顶端细胞壁中呈极性分布

POLAR-DISTRIBUTION OF CALCIUM IONS IN THE CELL WALL OF HYPHAL TIPS OF SAPROLEGNIA FERAX

焦锑酸钾处理的水霉(Saprolegnia ferax)菌丝显示:焦锑酸沉淀颗粒仅存在菌丝细胞壁而不是原生质中,并呈顶端到基部的极性分布,即在菌丝最顶端细胞壁中丰富致密、重叠在一起,在约3—10μm的亚顶端则变得稍为稀薄而可分辨,在约10μm以后的成熟区域进一步显得松散而无规律。焦锑酸沉淀颗粒可经EGTA螫合处理去除,并经X-射线微区分析证明在3.6—3.7keV区域可产生Sb和Ca元素混合峰,说明焦锑酸沉淀反映了Ca^(2+)的分布。对冷冻干燥菌丝细胞壁表面进行扫描电镜X-射线微区分析,同样证明菌丝细胞壁含有大量的Ca,菌丝最顶端Ca信号强度高于10μm以后的成熟区。由于Ca^(2+)和H^+可能为一对拮抗因子维持菌丝顶端细胞壁可塑性和刚性间的平衡以保证菌丝顶端生长,我们检验了菌丝生长过程中培养介质的pH变化,证实培养介质pH随培养时间的延长而逐渐下降。上述结果提示细胞壁Ca^(2+)可能在菌丝顶端生长过程中起作用。

This paper reported that antimonate precipitates existed only in the cell wall rather than the protoplasm and showed a tip to base gradient in the cell wall of hyphal tips of Saprolegnia ferax treated with potassium pyroantimonate, i. e., the granular precipitates showed very rich, dense and overlapping in the extreme apical zone, then became a little thin and resolvable in the sub-apical zone between about 3-10μm. and finally appeared very loose and irregular in mature zone beyou-nd about 10μm. Antimonate precipitates in hyphal tips could be removed with EGTA and examined to give the overlapping Ca/Sb peaks in 3.6-3.7KeV area by energy-dispersive X-ray analyzer coupled to TEM. Thus antimonate precipitates in cell wall reflected the distribution of Ca2+ in hyphal tips. Analysing the surface of cell wall of freezze-dried hyphal tip with energy-dispersive X-ray analyzer coupled to SEM, it was also found that cell walls of hyphae contained a large amount of Ca2+ and the intensity of Ca signal in the extreme apex was stronger than sub apex. Considering that Ca2+ and H+ may be one pair of antagonistic factors in maintenance of the balance between plasticity and rigidity of the cell wall to assure tip growth of hyphae, we examined changes of pH in medium during cultivation of hyphae and proved that pH in medium gradually reduced with the cultivation time. Above results suggested that Ca2+ in the cell wall of hyphal tips may play an important role in the tip growth of hyphae.