Genome-wide identification of SsJAZ gene family in sugarcane and function analysis of ScJAZ1/2 in drought stress response and flowering regulation

The JASMONATE ZIMDOMAIN (JAZ) proteins are key inhibitors of the jasmonate signaling pathway that play an important role in the regulation of plant growth and development and environmental stress responses. However, there is no systematic identification and functional analysis of JAZ gene family members in sugarcane. In this study, a total of 49 SsJAZ genes were identified from the wild sugarcane species Saccharum spontaneum genome that unevenly distributed on 13 chromosomes. Phylogenetic analysis showed that all SsJAZ members can be divided into six groups, and most of the SsJAZ genes contain photoreactive and ABA-responsive elements. RNA-seq analysis revealed that SsJAZ1-1/2/3/4 and SsJAZ7-1 were significantly upregulated under drought stress. The transcript level of ScJAZ1 that is the homologous gene of SsJAZ1 in modern sugarcane cultivars was upregulated by jasmonate acid (JA), PEG, and abscisic acid (ABA). Moreover, ScJAZ1 can interact with three other JAZ proteins to form heterodimers. The spatial and temporal expression analysis showed that SsJAZ2-1/2/3/4 were highly expressed in different tissues and growth stages and during the day-night rhythm between 10:00 and 18:00. Overexpression of ScJAZ2 in Arabidopsis accelerated flowering through activating the expression of AtSOC1, AtFT, and AtLFY. Moreover, the transcription level of ScJAZ2 were about 30-fold in early-flowering sugarcane variety than that of non-flowering variety, indicating ScJAZ2 positively regulated flowering. This first systematic analysis of JAZ gene family and function analysis of ScJAZ1/2 in sugarcane provide key candidate genes and lay the foundation for sugarcane breeding.