Differences in Ovary Development Between <i>Nymphaea</i> ‘Bull’s Eye’ and <i>Nymphaea</i> ‘King of Siam’ after Pollination
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Chinese Journal of Tropical Crops ›› 2022, Vol. 43 ›› Issue (4): 829-839.DOI: 10.3969/j.issn.1000-2561.2022.04.019

• Plant Cultivation, Physiology & Biochemistry • Previous Articles     Next Articles

Differences in Ovary Development Between Nymphaea ‘Bull’s Eye’ and Nymphaea ‘King of Siam’ after Pollination

TANG Yuwei1(), LI Jiahui1, MAO Liyan1, HUANG Qiuwei1, LONG Lingyun1, YU Yanping1, SU Qun2   

  1. 1. Guangxi Subtropical Crop Research Institute, Nanning, Guangxi 530001, China
    2. Flower Research Institute, Guangxi Academy of Agricultural Sciences, Nanning, Guangxi 530007, China
  • Received:2021-10-15 Revised:2021-11-26 Online:2022-04-25 Published:2022-04-24

Abstract:

Nymphaea (water lily) is an aquatic flower that has been introduced in recent years in our country. In particular, double petal water lily are very popular and full of love and attention by water lily lovers and breeders. And it has been increasingly widely used in the field of aquatic garden landscapes. But in the process of breeding, breeders often encounter the situation of failed hybridization. This makes it hard for breeders to breed double flower. In order to study on the reason that double petal water lily is difficult to set fruit, we selected the more representative cultivar Nymphaea ‘King of Siam’ from double petal water lily as the experimental group, and the better fertile cultivar Nymphaea ‘Bull’s Eye’ as the control group. Firstly, the microstructure of ovaries at different stages after pollination was compared by paraffin section technique. Secondly, the stigmas and ovules were further observed by scanning electron microscope. Finally, the differences of gene expression between developing and abortive ovary were analyzed by RNA-Seq. The results showed that multicellular uniserial papillae were distributed on the stigma surface of the two water lily varieties, and a circle of grooves were formed at the junction between single cells. The number of papillae was large and closely arranged. We think this structure can more easily capture foreign pollen. Meanwhile, after 7 days of N. ‘Bull’s Eye’ pollination, most of the ovules developed into red seeds, 10 days later, the ovary expanded into fruit, and the seed coat changed from red to black to form mature seeds. On the other hand, after 7 days of pollination, no seeds were formed in N. ‘King of Siam’. However, some ovules in its ovary develop, and its epidermis turns red. The morphological characteristics are similar to the red ovules after 4 days of N. ‘Bull’s Eye’ pollination. Therefore, we speculate that a small number of ovules may have completed fertilization, but can not develop further. Than, the ovary was completely aborted after 10 days. Microstructural observation showed that there were significant differences in ovule development between the two varieties after 7 days of pollination. The ovules of N. ‘Bull’s Eye’ increased significantly, and the zygotes began to form embryos, while the nucellus in the ovules of N. ‘King of Siam’ shrank and the ovules gradually disappeared. After 10 days of pollination, the embryo of N. ‘Bull’s Eye’ began to develop and further changed to seed morphology. In additional, the enrichment analysis of differential genes showed that photosynthesis antenna protein, photosynthesis, porphyrin and chlorophyll metabolism, ribosome, starch and sucrose metabolism may be the key pathways affecting the development of waterlily ovary. Consequently, we speculate that the abortion of the ovary of N. ‘King of Siam’ may be due to the inhibition of its own photosynthesis, which affects the production of nutrients such as sucrose and starch.

Key words: Nymphaea, cross pollination, ovary development, ovule, transcriptome

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