In this study, the causal gene for the purple color of pulvinus and leaf sheath (PPLS) trait, PPLS1, was cloned from F2 population constructed with "Shi-Li-Xiang" of high resistance to rust and purple color in pulvinus and leaf sheath as male parent. It was firstly elucidated that PPLS1 interacts with SiMYB85 to control the color of pulvinus and leaf sheath by regulating anthocyanin biosynthesis in foxtail millet. This study laid a theoretical foundation for screening authentic hybrids in foxtail millet crossing, especially for the efficient utilization of the rust resistant resource "Shi-Li-Xiang" with purple leaf sheath phenotype.

The representative paper is "the bHLH transcription factor PPLS1 regulates the color of pulvinus and leaf sheath in foxtail mile (Setaria italica)", which was published in《Theoretical and Applied Genetics》on March 10, 2020. Hui Bai is the first author, Zhiping Dong and Dayong Li are the corresponding authors, and Institute of Millet Crops of Hebei Academy of Agriculture and Forestry Sciences is the communication unit.

Abstract: Foxtail millet (Setaria italica), a self-pollinated crop with numerous small florets, is difficult for cross-pollination. The color of pulvinus and leaf sheath with purple being dominant to green is an indicative character, and often used for screening authentic hybrids in foxtail millet crossing. Deciphering molecular mechanism controlling this trait would greatly facilitate genetic improvement of cultivars in foxtail millet. Here, using the F2 bulk specific-locus amplified fragment sequencing approach, we mapped the putative causal gene for the purple color of pulvinus and leaf sheath (PPLS) trait to a 100 Kb region on chromosome 7. Expression analyses of the 15 genes in this region revealed that Seita.7G195400 (renamed here as PPLS1) was differentially expressed between purple and green cultivars. PPLS1 encodes a bHLH transcription factor and is localized in the nucleus with a transactivation activity. Furthermore, we observed that expression of a MYB transcription factor gene, SiMYB85 (Seita.4G086300) involved in anthocyanin biosynthesis, shows a totally positive association with that of PPLS1. Heterologous co-expression of both PPLS1 and SiMYB85 in tobacco leaves led to elevated anthocyanin accumulation and expression of some anthocyanin-related genes. Furthermore, PPLS1 physically interacts with SiMYB85. Taken together, our results suggest that PPLS1 interacts with SiMYB85 to control the color of pulvinus and leaf sheath by regulating anthocyanin biosynthesis in foxtail millet.

Contact: Hui Bai: Tel: +86-311-87670721 E-mail: baihui_mbb@126.com

Figure 1 a-c Color variation and pigments content of the two parental lines, Shi-Li-Xiang (SLX) and Yugu1 (YG1). d Color variations of pulvinus and leaf sheath in the two parental lines and their F2 population at heading stage. e The SNP_index association analysis on chromosome 7.