Plant Beneficial Deep-Sea Actinobacterium, Dermacoccus abyssi MT1.1T Promote Growth of Tomato (Solanum lycopersicum) under Salinity Stress

Simple Summary Salt stress is an important environmental problem that negatively affects agricultural and food production in the world. Currently, the use of plant beneficial bacteria for plant growth promotion is attractive due to the demand for eco-friendly and sustainable agriculture. In this study, salt tolerant deep-sea actinobacterium, Dermacoccus abyssi MT1.1(T) was investigated plant growth promotion and salt stress mitigation in tomato seedlings. In addition, D. abyssi MT1.1(T) whole genome was analyzed for plant growth promoting traits and genes related to salt stress alleviation in plants. We also evaluated the biosafety of this strain on human health and organisms in the environment. Our results highlight that the inoculation of D. abyssi MT1.1(T) could reduce the negative effects of salt stress in tomato seedlings by growth improvement, total soluble sugars accumulation and hydrogen peroxide reduction. Moreover, this strain could survive and colonize tomato roots. Biosafety testing and genome analysis of D. abyssi MT1.1(T) showed no pathogenicity risk. In conclusion, we provide supporting evidence on the potential of D. abyssi MT1.1(T) as a safe strain for use in plant growth promotion under salt stress. Salt stress is a serious agricultural problem threatens plant growth and development resulted in productivity loss and global food security concerns. Salt tolerant plant growth promoting actinobacteria, especially deep-sea actinobacteria are an alternative strategy to mitigate deleterious effects of salt stress. In this study, we aimed to investigate the potential of deep-sea Dermacoccus abyssi MT1.1(T) to mitigate salt stress in tomato seedlings and identified genes related to plant growth promotion and salt stress mitigation. D. abyssi MT1.1(T) exhibited plant growth promoting traits namely indole-3-acetic acid (IAA) and siderophore production and phosphate solubilization under 0, 150, 300, and 450 mM NaCl in vitro. Inoculation of D. abyssi MT1.1(T) improved tomato seedlings growth in terms of shoot length and dry weight compared with non-inoculated seedlings under 150 mM NaCl. In addition, increased total soluble sugar and total chlorophyll content and decreased hydrogen peroxide content were observed in tomato inoculated with D. abyssi MT1.1(T). These results suggested that this strain mitigated salt stress in tomatoes via osmoregulation by accumulation of soluble sugars and H2O2 scavenging activity. Genome analysis data supported plant growth promoting and salt stress mitigation potential of D. abyssi MT1.1(T). Survival and colonization of D. abyssi MT1.1(T) were observed in roots of inoculated tomato seedlings. Biosafety testing on D. abyssi MT1.1(T) and in silico analysis of its whole genome sequence revealed no evidence of its pathogenicity. Our results demonstrate the potential of deep-sea D. abyssi MT1.1(T) to mitigate salt stress in tomato seedlings and as a candidate of eco-friendly bio-inoculants for sustainable agriculture.

Automated summary

In this study, the salt stress mitigation and plant growth promotion potential of a deep-sea actinobacterium, Dermacoccus abyssi MT1.1(T), in tomato seedlings were investigated. The results showed that the inoculation of D. abyssi MT1.1(T) could improve tomato seedlings growth under salt stress by increasing soluble sugars and reducing hydrogen peroxide content. The biosafety testing and genome analysis confirmed the safety of this strain. Overall, these findings suggest that D. abyssi MT1.1(T) has the potential to be used as a safe bio-inoculant for promoting plant growth under salt stress.