GmCOL4-GmZTL1 interaction co-regulates GmSBH1 to improve seed deterioration under high temperature and humidity stress and affect leaf development

BBX transcription factors have a transcriptional regulatory role in response to light, circadian cues, and brassinosteroid-light crosstalk signaling. However, the functions of BBX in soybean resistance to seed deterioration have not been shown. In our previous study, a soybean gene GmSBH1 and a HSE cis-element of GmSBH1 promoter were found in response to high temperature and humidity (HTH) stress. GmCOL4 was a candidate protein, which bound to HSE cis-element. In the present study, GmCOL4 was isolated and characterized. Subcellular localization and transcriptional activation assays showed that GmCOL4 was a nuclear protein with transcriptional activation function. The BBOX2 domain was found to play an obvious role in transcriptional activation activity of GmCOL4. Furthermore, GmCOL4 interacted with GmZTL1 was confirmed in vivo and in vitro. GmCOL4 and GmZTL1 presented different expression patterns among diverse soybean tissues and were synergistically involved in response to HTH stress in developing seeds. Overexpression of GmCOL4 and GmZTL1 could alter tobacco phenotypes and enhance developing seed tolerance to seed deterioration under HTH stress. Based on these results, a regulation network was conjectured, GmCOL4 interacts with GmZTL1 to co-regulate the GmSBH1 via directly binding to the HSE cis-element, thereby enhancing the soybean resistance to seed deterioration under HTH stress and affecting leaf development.