AUTHOR=Jiang Lingmin , Peng Yuxin , Kim Ki-Hyun , Jeon Doeun , Choe Hanna , Han Ah-Reum , Kim Cha Young , Lee Jiyoung 

TITLE=Jeongeuplla avenae gen. nov., sp. nov., a novel β-carotene-producing bacterium that alleviates salinity stress in Arabidopsis

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1265308

DOI=10.3389/fmicb.2023.1265308

ISSN=1664-302X

ABSTRACT=<p>A novel endophytic bacterium, designated DY-R2A-6<sup>T</sup>, was isolated from oat (<italic>Avena sativa</italic> L.) seeds and found to produces β-carotene. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain DY-R2A-6<sup>T</sup> had 96.3% similarity with <italic>Jiella aquimaris</italic> LZB041<sup>T</sup>, 96.0% similarity with <italic>Aurantimonas aggregate</italic> R14M6<sup>T</sup> and <italic>Aureimonas frigidaquae</italic> JCM 14755<sup>T</sup>, and less than 95.8% similarity with other genera in the family <italic>Aurantimonadaceae</italic>. The complete genome of strain DY-R2A-6<sup>T</sup> comprised 5,929,370 base pairs, consisting of one full chromosome (5,909,198 bp) and one plasmid (20,172 bp), with a G + C content was 69.1%. The overall genome-related index (OGRI), including digital DNA–DNA hybridization (&lt;20.5%), ANI (&lt;79.2%), and AAI (&lt;64.2%) values, all fell below the thresholds set for novel genera. The major cellular fatty acids (&gt;10%) of strain DY-R2A-6<sup>T</sup> were C<sub>16:0</sub>, C<sub>19:0</sub> cyclo ω8c, and summed feature 8 (C<sub>18:1</sub>ω7c and/or C<sub>18:1</sub>ω6c). Ubiquinone-10 was the main respiratory quinone. We identified the gene cluster responsible for carotenoid biosynthesis in the genome and found that the pink-pigment produced by strain DY-R2A-6<sup>T</sup> is β-carotene. In experiment with Arabidopsis seedlings, co-cultivation with strain DY-R2A-6<sup>T</sup> led to a 1.4-fold increase in plant biomass and chlorophyll content under salt stress conditions, demonstrating its capacity to enhance salt stress tolerance in plants. Moreover, external application of β-carotene to Arabidopsis seedlings under salt stress conditions also mitigated the stress significantly. Based on these findings, strain DY-R2A-6<sup>T</sup> is proposed to represent a novel genus and species in the family <italic>Aurantimonadaceae</italic>, named <italic>Jeongeuplla avenae</italic> gen. nov., sp. nov. The type strain is DY-R2A-6<sup>T</sup> (= KCTC 82985<sup>T</sup> = GDMCC 1.3014<sup>T</sup>). This study not only identified a new taxon but also utilized genome analysis to predict and confirm the production of β-carotene by strain DY-R2A-6<sup>T</sup>. It also demonstrated the ability of this strain to enhance salt stress tolerance in plants, suggesting potential application in agriculture to mitigate environmental stress in crops.</p>