Water submergence is a major environmental stress that has detrimental effects on plant growth and survival. As an aquatic plant, lotus (Nelumbo nucifera) is widely cultivated in flood-prone lowlands throughout Asian countries. It is constantly challenged by the rising incidence of adverse weather events such as heavy rain. As a consequence, lotus may suffer long time flooding, even complete submergence. Therefore, it is urgent to study the endurance and acclimation mechanisms of lotus to complete submergence.

Dr. DENG Xianbao and YANG Dong, together with other coauthors of the Lotus Resources and Genetics Improvement Group of Wuhan Botanical Garden, reported the key response strategies of lotus to complete submergence. Time-course complete submergence treatments were conducted in two lotus varieties of ‘Qiuxing’ and ‘China Antique’.

Study revealed that the two lotus varieties had low tolerance to complete submergence, with a median lethal time about 10 days. Lotus plants under complete submergence took obviously the low oxygen “escape” strategy (LOES), with thinned leaves, rapidly elongated petioles, and high density of aerenchyma. Gene sets relevant to LOES, such as NnERF-VII genes, were quickly induced by submergence. In addition, genes involved in lotus innate immunity and reactive oxygen species (ROS) scavenging were also adjusted, to favor the lotus adaptation to complete submergence. Data also suggested the possible role of jasmonic acid in mediating lotus submergence response.

These results reveal for the first time that the LOES strategy is predominantly adopted in lotus to cope with submergence-induced complex stresses, and it will improve the understanding of the diverse mechanisms of plants response to submergence, and provide valuable genetic sources for breeding lotus cultivars with submerge tolerance.

Results, entitled with “Time-course analysis and transcriptomic identification of key response strategies to complete submergence in Nelumbo nucifera”, have been published online in Horticulture Research. This research was supported by funds received from the National Science Foundation of China, Key Research Program of Frontier Science CAS, and the Youth Innovation Promotion Association, CAS.

 Lotus plants take primarily the low-oxygen escape strategy. Genes encoding ACC synthases (a), Ethylene marker protein NnERF1 (b), and expansions (NnEXPs) (c) were significantly up-regulated. (d) Lotus under complete submergence developed dramatically elongated petioles. (e-l), lotus leaf and petiole contain high density aerenchyma under complete submergence (Image by WBG)