Lotus (Nelumbo) is a basal eudicot with agricultural and horticultural values. It is a worldwide aquatic ornamental belonging to the Nelmbonaceae family with only two species, N. lutea with yellow flowers and N. nucifera with red or white flowers. Although it is the most important trait in ornamental lotus, the genetic mechanism underlying the flower color difference in Nelumbo has not been fully characterized.

Under the supervision of Prof. YANG Mei and Prof. YANG Dong from the Wuhan Botanical Garden of the Chinese Academy of Sciences, researchers identified NnMYB5 as the key gene controlling petal color in N. nucifera by quantitative trait locus mapping and bulked segregant analysis (BSA) sequencing.

Transcriptome analysis, dual-luciferase and yeast one-hybrid assays showed that NnMYB5 can directly activate the anthocyanin transporter gene GLUTATHIONE S-TRANSFERASE2 (NnGST2).

This study shows that an 80-kb deletion harboring NnMYB5 in the white petals of N. nucifera inactivates the expression of NnGST2, thereby blocking anthocyanin accumulation in the petals.

This causal mutation leading to anthocyanin deficiency in the white N. nucifera differs from that in N. lutea, which is caused by pseudogenicity of NnMYB5, indicating that two independent mutations on NnMYB5 control color variation among Nelumbo species.

The results provide new insights into the regulatory roles of NnMYB5 in enhancing anthocyanin accumulation in N. nucifera petals, 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.

This study was published in Plant Physiology entitled "Transcription factor NnMYB5 controls petal color by regulatingGLUTATHIONE S-TRANSFERASE2inNelumbo nucifera" and it was supported by the Biological Resources Programme, CAS and the National Natural Science Foundation of China.

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