Microbe-enhanced high light stress tolerance of Arabidopsis thaliana photosynthesis is coordinated through Iron-dependent redox metabolism

High light stress in subtropical and tropical regions strongly limits agricultural production due to photo-oxidative damage, decreased growth and yield. Here, we investigated whether beneficial microbes can protect plants under high light stress. We show that Enterobacter sp. SA187 (SA187) assists Arabidopsis in maintaining growth under high light stress, reducing the accumulation of reactive oxygen species (ROS) and maintaining photosynthesis. Under high light stress, SA187 induces dynamic transcriptional changes related to a fortified iron metabolism and redox system in Arabidopsis. A genetic analysis shows that SA187-induced plant high light stress tolerance is mediated by ethylene signaling via the transcription factor EIN3 to enhance iron metabolism. In summary, we show that Arabidopsis interaction with SA187 results in sustained photosynthesis under high light stress suggesting that beneficial microbes could be effective and cheap means for enhancing high light stress tolerance in crops. Overall design: Arabidopsis thaliana plants were grown at 22°C under 16 h light and 8 h dark period Two different light stress regimes (normal light 130 µmol m-2 s-1 and high light 1050 µmol m-2 s-1 ) were implemented on SA187 colonized plants Total RNA was extracted using Nucleospin RNA plant kit (Macherey-Nagel), we further followed with DNaseI treatment to remove gemomic DNA as per manufacturer's instructions. RNA libraries were prepared for sequencing using standard Ribo-zero Illumina protocol RNA-seq was carried out on three independent biological replicates (except two samples)