水稻花器细胞壁超微结构与稻曲病菌的选择性侵染分析

Relationship between Ultrastructure of Cell Walls of Rice Spikelets and Infection Specificity of Villosiclava virens

为了探明稻曲病菌选择性侵染水稻花丝组织和浆片的细胞生物学机制,该研究以高度感病的‘甬优12号’水稻品种为材料,于孕穗期开始每间隔2d取样,同时在旗叶与倒二叶叶枕距离1~2cm时进行人工接种并在接种后5、10和15d时分别取样,对开花前后水稻不同花器官细胞的超微结构以及稻曲病菌侵染位点进行比较分析。结果显示:(1)在开花过程中,水稻花丝可伸长4~6倍,水稻花丝的所有组织细胞均能够均匀纵向伸长,且未发现细胞断裂出现的空腔;水稻浆片细胞在开花时吸水,横向膨胀约1倍,但浆片维管束的环纹导管环纹间距离没有明显变化;超微结构观察发现,大部分浆片细胞呈现细胞膨胀过程,只有浆片上部外围细胞具有一定伸长能力;水稻子房及柱头等在开花过程中其长度及体积未发现明显变化。(2)水稻花丝细胞壁的微纤丝排列比较疏松,透射电镜下单个微纤丝束清晰可辨,而子房和花药等器官的细胞壁结构致密,无法分辨单个微纤丝束。(3)稻曲病菌可在花丝中沿细胞间隙和细胞壁中层生长,但在浆片中菌丝主要被限制在细胞间隙中生长,说明花丝与浆片的细胞中层组分与结构存在差异。(4)细胞化学分析显示,花丝细胞壁纤维素含量较少,且不含有β-1,3-葡聚糖。研究表明,水稻花器细胞壁结构相对疏松及其细胞壁中层的结构特性和组分与稻曲病菌的选择性侵染具有密切相关关系。

The fungus Villosiclava virens infects dominantly rice stamen filaments and some lodicules resulting in rice false smut. Here we examine the ultrastructures of the cell walls of various organs in rice spikelets around the anthesis to explore the specificity for infection. The inoculation was performed in rice cultivar, ‘Yongyou 12’, a high susceptible cultivar, and the infected spikelets were sampled at 5, 10, and 15 days after inoculation. The results showed that： （1） the stamen filament cells could elongate integrally for 4-6 folds, and the peripheral cells in top of lodicula could elongate significantly during flowering. （2） Microfibrils in those cell walls arranged loosely and could be clearly distinguished with transmission electronic microspcope. Conversely, the cell walls in ovaries, stigmas, and anthers were compact and the microfibrils could not be discerned. （3） The pathogen could grow in different orientations in both cell gaps and cell wall middle lamella in the stamen filaments, but its extension in the lodicula was limited mainly in cell gaps. This indicates that the structure and components of middle lamella in filaments and lodicula are different. （4） Cytochemical labeling revealed that there was less cellulose and no β 1,3 glucane in the cell walls of stamen filaments. These suggest that the ultrastructure and components in cell walls and middle lamella in various organs in rice spikelets are highly related to the specificity of infection by the pathogen .