Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Plant Cell Rep. 2020 Jul;39(7):861-872. doi: 10.1007/s00299-020-02535-x. Epub 2020 Apr 8.
The cytokinin pathway promotes the initiation of bulbil formation, and iPA may an important type of cytokinin during bulbil formation in Lilium lancifolium. Bulbils are important vegetative reproductive organs in triploid Lilium lancifolium. We previously showed that cytokinins are involved in bulbil formation, but how cytokinins participate in bulbil formation is not clear. In this study, bulbil formation was divided into three stages on the basis of anatomical and histological observations: the bulbil initiation stage, bulbil primordium-formation stage and bulbil structure-formation stage. The results indicated that iPA was the most critical cytokinin during the bulbil initiation. qRT-PCR revealed that increased iPA content during bulbil initiation was mainly due to increased expression of cytokinin synthesis genes (IPT1/5) and cytokinin activation genes (LOG1/3/5/7) and significantly decreased expression of the cytokinin degradation gene CKX4. Exogenous 6-BA and lovastatin affected the cytokinin pathway and promoted or inhibited bulbil initiation by increasing or decreasing the content of endogenous iPA, respectively. In summary, we demonstrate that cytokinins positively regulate bulbil formation and provide preliminary insight into the regulatory mechanisms by which the cytokinin pathway promotes bulbil initiation.
细胞分裂素途径促进小鳞茎形成，异戊烯基腺嘌呤（iPA）可能是百合小鳞茎形成过程中一种重要的细胞分裂素。小鳞茎是三倍体百合重要的营养繁殖器官。我们之前的研究表明细胞分裂素参与了小鳞茎的形成，但细胞分裂素如何参与小鳞茎的形成尚不清楚。本研究根据解剖学和组织学观察将小鳞茎的形成过程分为三个阶段：小鳞茎起始阶段、小鳞茎原基形成阶段和小鳞茎结构形成阶段。结果表明，在小鳞茎起始阶段，iPA 是最关键的细胞分裂素。qRT-PCR 显示，小鳞茎起始过程中 iPA 含量的增加主要归因于细胞分裂素合成基因（IPT1/5）和细胞分裂素激活基因（LOG1/3/5/7）表达的增加，以及细胞分裂素降解基因 CKX4 表达的显著降低。外源 6-BA 和 lovastatin 通过增加或减少内源 iPA 的含量，影响细胞分裂素途径，促进或抑制小鳞茎的起始。综上所述，我们证明了细胞分裂素正向调控小鳞茎的形成，并为细胞分裂素途径促进小鳞茎起始的调控机制提供了初步的见解。
