Lotus (Nelumbo nucifera) is an emergent aquatic plant that is widely cultivated in 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 collaborator at the Wuhan Botanical Garden of the Chinese Academy of Sciences (CAS), have reported the key response strategies of lotus to complete submergence by conducting time-course complete submergence in two lotus varieties 'Qiuxing' and 'China Antique'.  

According to the researchers, 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 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, for the first time, reveal 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 have been published in Horticulture Research in an article entitled "Time-course analysis and transcriptomic identification of key response strategies to complete submergence in Nelumbo nucifera."

This research was supported by the National Science Foundation of China, the Key Research Program of Frontier Science of CAS, and the Youth Innovation Promotion Association of 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)