Molecular breeding of water lily: engineering cold stress tolerance into tropical water lily

Cuiwei Yu,Mingying Liu,Renying Zhuo,Fei Chen,Yan Shen,Shirong Zhou,Jing Jiang,Guirong Qiao,Guanchun Yu,Yuchu Chen,Wenmin Qiu,Liangsheng Zhang,Dongbei Yu,Xiaojiao Han

doi:10.1038/s41438-018-0086-2

Abstract

Water lilies (order Nymphaeales) are rich in both economic and cultural values. They grow into aquatic herbs, and are divided into two ecological types: tropical and hardy. Although tropical water lilies have more ornamental and medicinal values compared to the hardy water lily, the study and utilization of tropical water lilies in both landscaping and pharmaceutical use is greatly hindered due to their limited planting area. Tropical water lilies cannot survive the winter in areas beyond 24.3°N latitude. Here, the transgenic pipeline through the pollen-tube pathway was generated for water lily for the first time. To improve cold stress tolerance of tropical water lilies, a gene encoding choline oxidase (CodA) driven by a cold stress-inducible promoter was transformed into a tropical water lily through the pollen-tube transformation. Six independent transgenic lines were tested for survival rate during two winter seasons from 2015 to 2017 in Hangzhou (30.3°N latitude). PCR and southern blot detection revealed that the CodA gene had been integrated into the genome. Reverse transcription PCR showed that CodA gene was induced after cold stress treatment, and further quantitative real-time PCR revealed different expressions among six 4 lines and line 3 had the highest expression. Multiple physiological experiments showed that after cold stress treatment, both the conductivity and malondialdehyde (MDA) levels from transgenic plants were significantly lower than those of non-transgenic plants, whereas the content of betaine and the activity of superoxide dismutase, catalase, and peroxidase were higher than those from non-transgenic plants. These results suggest that expression of exogenous CodA gene significantly improved the cold stress tolerance of tropical water lilies through a wide range of physiological alterations. Our results currently expanded a six-latitude cultivating area of the tropical water lilies. These results not only illuminate the bright future for water lily breeding but will also facilitate the functional genomic studies.

Highlights

Water lily is a common name for all plants categorized into the order Nymphaeales
To compare the performance among the six lines at the 24-h cold stress point, Quantitative real-time PCR (qRT-PCR) detection of the six lines suggests that line 3 (L3) has a significant higher expression than the other lines, whereas L5 had a significant lower expression than the L1 and L3 lines (Fig. 5f). These results indicate that choline oxidase (CodA) in the transformed plants had been successfully induced to express cold stress using the Rd29A promoter in the transformed tropical water lily
These results showed that the CodA gene had been stably integrated into all of the six lines

Summary

Introduction

Water lily is a common name for all plants categorized into the order Nymphaeales. Most of water lilies (more than 50 species) are categorized within the ornamental-Hydrocallis) and hardy water lily (Nymphaea spp.). Most of water lilies (more than 50 species) are categorized within the ornamental-. The tropical water lilies generally have higher ornamental and. The flowers of tropical water lily are rich in color, with red, yellow, white, blue, purple, and other complex color constitutions. Leaves of the tropical water lily are in reddish, purplish, or green color and vary in shape. Hardy water lilies only exhibit three petal colors: red, white, and yellow. Another phenotypic distinction between hardy and tropical water lilies is the lack of spots and serration in leaves of hardy water lily. The promotion of the tropical water lily is seriously limited by its inability to overwinter in north subtropical (24.3°N latitude) or more northern areas. Breeders have strong interest to expand the water lily market, by improving the cold stress tolerance of the tropical water lily so that it can overwinter in the cold areas

Methods

Results

Conclusion