AtBRO1, BRO1-like domain-containing protein, modulates growth and abiotic stress responses in Arabidopsis
Plants physiological mechanisms are affected by Abscisic acid (ABA) via changing gene expression and empowers plants to adapt in numerous environments. Plants have evolved their protection mechanisms for seed germination and abiotic environments to deal with critical harsh conditions. Here, we have explored those changes in Arabidopsis thaliana plants subjected to multiple abiotic stresses. AtBro1 transcripts showed up-regulation in the presence of salt, ABA and mannitol stress conditions. AtBRO1 over-expression lines exhibited robust tolerance to drought and salt stress. Further, ABA elicits resistance responses in loss-of-function bro1-1 mutant plants and AtBro1 positively regulates drought resistance in Arabidopsis. Promoter of AtBro1 fused with GUS showed GUS expression mainly in the rosette leaves and floral clusters, especially in anthers. AtBro1 protein was found to be localized in the plasma membrane of Arabidopsis at the subcellular level by using AtBro1::GFP fusion. Using a broad RNA-sequencing analysis, we observed that early transcriptional responses prompted by ABA induction exhibit specific quantitative differences at different time points, suggesting that ABA stimulates resistance responses in bro1-1 mutant plants. Additionally, transcripts levels of MOP9.5, MRD1, HEI10, and MIOX4 were altered in loss-of-function mutant plants which are involved in different stress conditions.  Collectively, our results have shown that AtBro1 is involved in a significant role by regulating plant transcriptional response to ABA and induction of resistance response against abiotic stress. Overall design: Seeds of WT Arabidopsis thaliana, Columbia ecotype (Col-0), as well as bro1-1 mutant were used in this study. After two days of stratification at 4°C, the plants were grown in Half Murashige and Skoog Basal Medium supplemented with sucrose. Seedlings were grown weeks for two weeks, then treated with ABA (100 µM) for 2 and 4 hours. The harvested plant materials were freezed in liquid nitrogen and stored in -80°C freezer until further use. For each condition (mock and ABA treated), three independent biological replicates were used and total RNA was extracted using RNAeasy kit (Qiagen) according to the manufacturer's protocol. And samples were used for mRNA sequencing.