Genome-wide identification of the MED25 BINDING RING-H2 PROTEIN gene family in foxtail millet (Setaria italica L.) and the role of SiMBR2 in resistance to abiotic stress in Arabidopsis.

The SiMBR genes in foxtail millet were identified and studied. Heterologous expression of SiMBR2 in Arabidopsis can improve plant tolerance to drought stress by decreasing the level of reactive oxygen species. Foxtail millet (Setaria italica L.), a C4 crop recognized for its exceptional resistance to drought stress, presents an opportunity to improve the genetic resilience of other crops by examining its unique stress response genes and understanding the underlying molecular mechanisms of drought tolerance. In our previous study, we identified several genes linked to drought stress by transcriptome analysis, including SiMBR2 (Seita.7G226600), a member of the MED25 BINDING RING-H2 PROTEIN (MBR) gene family, which is related to protein ubiquitination. Here, we have identified ten SiMBR genes in foxtail millet and conducted analyses of their structural characteristics, chromosomal locations, cis-acting regulatory elements within their promoters, and predicted transcription patterns specific to various tissues or developmental stages using bioinformatic approaches. Further investigation of the stress response of SiMBR2 revealed that its transcription is induced by treatments with salicylic acid and gibberellic acid, as well as by salt and osmotic stresses, while exposure to high or low temperatures led to a decrease in its transcription levels. Heterologous expression of SiMBR2 in Arabidopsis thaliana enhanced the plant's tolerance to water deficit by reducing the accumulation of reactive oxygen species under drought stress. In summary, this study provides support for exploring the molecular mechanisms associated with drought resistance of SiMBR genes in foxtail millet and contributing to genetic improvement and molecular breeding in other crops.