A mini foxtail millet with anArabidopsis-like life cycle as a C4model system

This study developedxiaomi, a mini foxtail millet mutant, as a C(4)model plant that has a short life cycle and small stature. To further enhance its model plant function,xiaomi's genome was sequenced and an efficient transformation system was established. Foxtail millet (Setaria italica) is an important crop species and an emerging model plant for C(4)grasses. However, functional genomics research on foxtail millet is challenging because of its long generation time, relatively large stature and recalcitrance to genetic transformation. Here we report the development ofxiaomi, a rapid-cycling mini foxtail millet mutant as a C(4)model system. Five to six generations ofxiaomican be grown in a year in growth chambers due to its short life cycle and small plant size, similar toArabidopsis. A point mutation in thePhytochrome C(PHYC) gene was found to be causal for these characteristics.PHYCencodes a light receptor essential for photoperiodic flowering. A reference-gradexiaomigenome comprising 429.94 Mb of sequence was assembled and a gene-expression atlas from 11 different tissues was developed. These resources, together with an established highly efficient transformation system and a multi-omics database, makexiaomian ideal model system for functional studies of C(4)plants.