β-Glucanases were found in the cell wall of Lilium longiflorum Thunb. pollen tubes grown in vitro . The activity of β-glucanases was, in a certain extent, decreased by nojirimycin, an inhibitor of glucosidase. Pollen germination percentage reduced dramatically when nojirimycin was applied in the culture medium. In case that nojirimycin was added at 0 or 1 h after the onset of incubation, the inhibition rate was 99.6% and 91.4%, respectively. When 3 mmol/L of nojirimycin was applied in the liquid medium at 0, 1, 1.5 and 2 h after the onset of incubation, the growth of pollen tubes was interrupted, which resulted in the morphological change of the pollen tubes such as the newly grown portion of pollen tubes being bent, curved and swollen. Tracing the growth pattern of the individual pollen tube grown in semi-solid medium by video microscopy, the authors demonstrated that pollen tube growth rate was strongly inhibited by nojirimycin at concentrations ranged from 0.003 to 3 mmol/L. Moreover, the cytoplasmic arrangement and the morphology of the pollen tubes were also affected by nojirimycin. The growth inhibition brought about by nojirimycin was reversible. These results indicated that β-glucanases, which degrade 1,3-β-glucan and/or 1,4-β-glucan or 1,3:1,4-β-glucan constructed in the cell wall, are involved in pollen germination and pollen tube growth. It provides new insight into an understanding of the contribution of β-glucanases to the cell wall extensibility and the crucial role of cell wall in regards to the regulation of pollen tube growth.
细胞壁结合的β-葡聚糖酶对百合花粉管顶端生长的调节作用
李一勤1 小竹敬久2 樱井直树2 赵南明3 刘强3
(1. 清华大学生物科学与技术系，北京100084；2. 广岛大学总和科学部环境研究系，东广岛739 ，日本；
3. 清华大学生物科学与技术系生物膜与膜生物工程国家重点实验室，北京100084）
摘要：从离体培养的麝香百合(LiliumlongiflorumThunb.)花粉管细胞壁中分离纯化出β-葡聚糖酶。抑制剂野尻酶素（nojirimycin）使该酶活性明显降低。若在百合花粉培养的初始或培养1h时加入3mmol/L野尻酶素，与对照相比较，花粉的萌发率分别被抑制99.6%和91.4%。若把3mmol/L野尻酶素分别在培养的不同时刻(0、1、1.5和2h)加入到液体培养基中,花粉管的生长都即刻受阻。此后，花粉管生长方向稍有改变，且花粉管直径略增，呈弯曲的非正常形态。用视频显微术跟踪记录在正常或含有不同浓度野尻酶素（0.003、0.03、0.3和3mmol/L）的半固体培养基中培养的花粉管的生长变化模式,发现该抑制剂明显降低花粉管的生长速率并影响其生长方向，而且花粉管直径、胞质内细胞器及囊泡的分布和顶端生长区的区域范围也呈现异常。野尻酶素对花粉管生长的抑制是可逆转的。这些结果表明，β-葡聚糖酶参与百合花粉的萌发和花粉管生长的调节。结合我们已报道的该酶的性质及作用方式，进而推测该酶通过降解1，3-/1，4-或1，3：1，4-β-葡聚糖，影响细胞壁的延展性，从而对花粉管顶端生长显示调节作用
关键词： 细胞壁；β-葡聚糖酶；麝香百合；花粉管；顶端生长；野尻酶素
全 文 ：