Fig. 7. A working model of VIG1 and OsbZIP18 mediated seedling vigor, chilling tolerance, and grain number per panicle.

VIG1 interacts with OsbZIP18 via the leucine zipper region (ZIP), and two proteins function synergistically in repressing the transcription of downstream genes involved in cell expansion, cell division, cold tolerance, and grain yield. Solid and dotted lines ending with a bar indicate direct and indirect repression, respectively. Red crosses indicate the blocked suppressive function of VIG1 and OsbZIP18. Dark green ellipses overlapped indicate the leucine zipper region (ZIP) of VIG1. The VIG1 and OsbZIP18 proteins with normal functions are indicated by the green and yellow circles, respectively. The vig1a and OsbZIP18 proteins with abnormal functions are indicated by the black circles, respectively. The vig1b protein is indicated by the gray circle. Green and gray seedlings represent survival and dead seedlings after chilling stress treatment, respectively. The number of wavy lines indicate the gene expression levels.