Yen Chih-Chung, Hsu Chia-Mei, Jiang Pei-Luen, Jauh Guang-Yuh
Institute of Plant and Microbial Biology, Academia Sinica, 11529, Taipei, Taiwan, ROC.
Department of Biotechnology, National Formosa University, Huwei Township, Yulin County, Taiwan.
Bot Stud. 2024 Jan 26;65(1):5. doi: 10.1186/s40529-024-00410-6.
Pollen germination is a crucial process in the life cycle of flowering plants, signifying the transition of quiescent pollen grains into active growth. This study delves into the dynamic changes within organelles and the pivotal role of autophagy during lily pollen germination. Initially, mature pollen grains harbor undifferentiated organelles, including amyloplasts, mitochondria, and the Golgi apparatus. However, germination unveils remarkable transformations, such as the redifferentiation of amyloplasts accompanied by starch granule accumulation. We investigate the self-sustained nature of amylogenesis during germination, shedding light on its association with osmotic pressure. Employing BODIPY 493/503 staining, we tracked lipid body distribution throughout pollen germination, both with or without autophagy inhibitors (3-MA, NEM). Typically, lipid bodies undergo polarized movement from pollen grains into elongating pollen tubes, a process crucial for directional growth. Inhibiting autophagy disrupted this essential lipid body redistribution, underscoring the interaction between autophagy and lipid body dynamics. Notably, the presence of tubular endoplasmic reticulum (ER)-like structures associated with developing amyloplasts and lipid bodies implies their participation in autophagy. Starch granules, lipid bodies, and membrane remnants observed within vacuoles further reinforce the involvement of autophagic processes. Among the autophagy inhibitors, particularly BFA, significantly impede germination and growth, thereby affecting Golgi morphology. Immunogold labeling substantiates the pivotal role of the ER in forming autophagosome-like compartments and protein localization. Our proposed speculative model of pollen germination encompasses proplastid differentiation and autophagosome formation. This study advances our understanding of organelle dynamics and autophagy during pollen germination, providing valuable insights into the realm of plant reproductive physiology.
花粉萌发是开花植物生命周期中的一个关键过程，标志着静止的花粉粒向活跃生长的转变。本研究深入探讨了百合花粉萌发过程中细胞器内的动态变化以及自噬的关键作用。最初，成熟花粉粒含有未分化的细胞器，包括造粉体、线粒体和高尔基体。然而，萌发过程中会出现显著的变化，例如造粉体的再分化伴随着淀粉粒的积累。我们研究了萌发过程中淀粉合成的自我维持性质，揭示了其与渗透压的关系。利用BODIPY 493/503染色，我们追踪了在有或没有自噬抑制剂（3-MA、NEM）的情况下整个花粉萌发过程中脂体的分布。通常，脂体会从花粉粒向伸长的花粉管进行极化运动，这一过程对定向生长至关重要。抑制自噬会破坏这种重要的脂体重新分布，强调了自噬与脂体动态之间的相互作用。值得注意的是，与发育中的造粉体和脂体相关的管状内质网（ER）样结构的存在意味着它们参与了自噬。液泡内观察到的淀粉粒、脂体和膜残余物进一步证实了自噬过程的参与。在自噬抑制剂中，特别是BFA，显著阻碍萌发和生长，从而影响高尔基体形态。免疫金标记证实了内质网在形成自噬体样区室和蛋白质定位中的关键作用。我们提出的花粉萌发推测模型包括前质体分化和自噬体形成。本研究推进了我们对花粉萌发过程中细胞器动态和自噬的理解，为植物生殖生理学领域提供了有价值的见解。
