Lotus (Nelumbo) is a basal eudicot with agricultural and horticultural values. It is a worldwide aquatic ornamental, belongs to the plant family Nelmbonaceae with only two species, N. lutea with yellow flowers and N. nucifera with red or white flowers. Despite being the most important trait in ornamental lotus, the genetic mechanism underlying flower color difference in Nelumbo is yet to be fully characterized.

Supervised by Prof. YANG Mei and Prof. YANG Dong from Wuhan Botanical Garden, researchers identified NnMYB5 as the key gene controlling petal color in N. nucifera by quantitative trait locus mapping and BSA-sequencing. Transcriptome analysis, dual-luciferase and yeast one-hybrid assays showed that NnMYB5 could directly activate the anthocyanin transporter gene GLUTATHIONE S-TRANSFERASE2 (NnGST2).

This study demonstrates that an 80-kb deletion harboring NnMYB5 in the white N. nucifera petals inactivates the expression of NnGST2, thereby blocking anthocyanin accumulation in petals. This causal mutation leading to anthocyanin deficiency in the white N. nucifera differes from that in N. lutea, which is caused by pseudogenicity of NnMYB5, indicating that two independent mutations on NnMYB5 controls color variants among Nelumbo species.

These results provide new insights into the regulatory roles of NnMYB5 in enhancing the N. nucifera petal anthocyanin accumulation, and establish a regulatory link between NnMYB5 and the anthocyanin transporter NnGST2 gene in lotus. In addition, it elucidates that two independent NnMYB5 mutations underlie flower coloration in Nelumbo.

Results have been published in the Plant Physiology entitled “Transcription factor NnMYB5 controls petal color by regulating GLUTATHIONE S-TRANSFERASE2 in Nelumbo nucifera”. This research was financially supported by the Biological Resources Programme, Chinese Academy of Sciences and the National Natural Science Foundation of China.

 Hypothetical model illustrating the genetic mechanism underlying petal color variation in Nelumbo (Image by WBG)