Wu Yun, Ren Ziming, Gao Cong, Sun Minyi, Li Shiqi, Min Ruihan, Wu Jian, Li Danqing, Wang Xiuyun, Wei Yanping, Xia Yiping
Genomics and Genetic Engineering Laboratory of Ornamental Plants, Department of Horticulture, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China.
Department of Landscape Architecture, School of Civil Engineering and Architecture, Zhejiang Sci-Tech University, Hangzhou, China.
Front Plant Sci. 2021 Jan 14;11:564713. doi: 10.3389/fpls.2020.564713. eCollection 2020.
In bulb crops, bulbing is a key progress in micropropagation and is the feature that most distinguishes bulbous crops from other plants. Generally, bulbing involves a shoot-to-bulblet transition; however, the underlying mechanism remains elusive. We explored this process by tracking the shoot-to-bulblet transition under different culture conditions. Rapid starch accumulation occurred at 15 days after transplanting (DAT) in the bulblet-inducing treatments as confirmed via histological observations and the significant elevation of starch synthesis related-gene transcription, including , , , , and . However, for shoots that did not transition to bulblets and maintained the shoot status, much higher soluble sugars were detected. Interestingly, we observed a clear shift from invertase-catalyzed to sucrose synthase-catalyzed sucrose cleavage pattern based on the differential expression of and during the key transition stage (prior to and after bulbing at 0-15 DAT). Shoots that transitioned into bulblets showed significantly higher expression, especially expression, than shoots that did not transition. A symplastic phloem unloading pathway at the bulblet emergence stage (15 DAT) was verified via the 6(5)-carboxyfluorescein diacetate fluorescent tracer. We propose that starch is the fundamental compound in the shoot-to-bulblet transition and that starch synthesis is likely triggered by the switch from apoplastic to symplastic sucrose unloading, which may be related to sucrose depletion. Furthermore, this study is the first to provide a complete inventory of the genes involved in starch metabolism based on our transcriptome data. Two of these genes, and , were verified by rapid amplification of cDNA ends cloning, and these data will provide additional support for research since whole genome is currently lacking.
在球茎作物中，鳞茎形成是微繁殖中的关键进程，也是球茎作物区别于其他植物的最显著特征。一般来说，鳞茎形成涉及从芽到小鳞茎的转变；然而，其潜在机制仍不清楚。我们通过追踪不同培养条件下从芽到小鳞茎的转变过程来探索这一进程。通过组织学观察以及淀粉合成相关基因转录的显著升高，包括 、 、 、 和 ，证实了在诱导小鳞茎形成的处理中，移植后15天（DAT）出现了快速的淀粉积累。然而，对于未转变为小鳞茎并维持芽状态的芽，检测到的可溶性糖含量要高得多。有趣的是，基于关键转变阶段（0 - 15 DAT鳞茎形成前后） 和 的差异表达，我们观察到蔗糖裂解模式从转化酶催化转变为蔗糖合酶催化的明显转变。转变为小鳞茎的芽比未转变的芽显示出显著更高的 表达，尤其是 的表达。通过6(5)-羧基荧光素二乙酸荧光示踪剂验证了小鳞茎出现阶段（15 DAT）的共质体韧皮部卸载途径。我们提出淀粉是从芽到小鳞茎转变的基本化合物，淀粉合成可能是由质外体蔗糖卸载向共质体蔗糖卸载的转变触发的，这可能与蔗糖耗尽有关。此外，本研究首次基于我们的转录组数据提供了参与淀粉代谢的基因的完整清单。其中两个基因， 和 ，通过cDNA末端快速扩增克隆进行了验证，由于目前缺乏全基因组数据，这些数据将为 研究提供额外支持。
