K型小麦雄性不育系绒毡层结构变化及相关基因的表达分析

为揭示K型小麦雄性不育系的败育时期和败育机制,以K型小麦雄性不育系K519A及其保持系519B为材料,采用半薄和超薄树脂切片法对花药绒毡层进行显微和亚显微结构观察,并对孢粉素转运相关基因RAFTIN1和绒毡层细胞降解相关基因APs在不同生育时期的表达模式进行分析。结果表明,与保持系相比,不育系花药绒毡层在四分体时期提前降解,部分绒毡层细胞脱离中层侵入药室内,发育至二核和三核期绒毡层细胞只剩下细胞轮廓和少量附着的乌氏体。不育系小孢子细胞壁在单核期开始增厚,是同时期保持系小孢子细胞壁厚度的2.35倍,发育至二核期小孢子细胞壁继续增厚,但三核期不育系小孢子细胞壁比保持系小孢子细胞壁薄,仅是保持系花粉粒细胞壁厚度的89%,并且三核期不育系花粉粒出现畸形和质壁分离的异常现象。自小孢子母细胞时期至单核期,不育系中RAFTIN1和APs基因的相对表达量都显著高于保持系,但在二核期不育系中的相对表达量显著低于保持系。推测K型小麦雄性不育系K519A的败育可能发生在四分体期和二核期。RAFTIN1和APs基因的表达模式与细胞学观察结果相契合,故推测这两个基因很可能参与了K型不育系K519A的不育过程。

Change of Tapetum Structure and Related Gene Expression in K-type Male Sterile Wheat

The objective of this study was to gain an insight into the abortion mechanism of K-type cytoplastic male sterile (CMS) line of wheat. The microstructure and ultrastructure of tapetum of the K-type CMS line,K519A,and its maintainer 519B were observed with semithin and ultrathin sections. The expression patterns of tapetal-related genes, RAFTIN1 and APs,during microspore development were also analyzed. The tapetum of K519A degenerated at tetrad stage,which is earlier than 519B. Partial tapetal cells entered the anther chamber,and only cell contour and a small amount of ubisch bodies were observed at binuclear and trinuclear stages. The cell wall of microspore of K519A were thicker than that of 519B at mononuclear (2.35 folds more than that of 519B) and binuclear stage,but became thinner than that of 519B at trinuclear stage (0.89 fold of that of 519B). Besides,abnormal pollen grains and plasmolysis were observed in K519A at trinuclear stage. From microspore mother cell to mononuclear stage,the relative expression levels of RAFTIN1 and APs were significantly higher in K519A than in 519B,but significantly lower in K519A at binuclear stage. These results indicate that sterility of K519A probably occurs at tetrad and binuclear stage. The abortion might be related to the abnormal tapetal structure,resulting that partial tapetal cells intrude into the chamber and occupy the room for the normal development of microspore at tetrad stage. The early degradation of tapetal cells causes thickening of cell wall at mononuclear stage by consuming energies and less synthesis of sporopollenin at binuclear and later stages due to energy deficiency. As a result,the microspore cell wall becomes thinner in the sterile line than that in the maintainer line at trinuclear stage and pollen abortion eventually. This hypothesis can be validated by the expression analysis of RAFTIN1 and APs genes,and the two genes are considered to be involved in the sterile process of K519A.