Two Novel Plant-Growth-Promoting Lelliottia amnigena Isolates from Euphorbia prostrata Aiton Enhance the Overall Productivity of Wheat and Tomato

Euphorbiaceae is a highly diverse family of plants ranging from trees to ground-dwelling minute plants. Many of these have multi-faceted attributes like ornamental, medicinal, industrial, and food-relevant values. In addition, they have been regarded as keystone resources for investigating plant-specific resilience mechanisms that grant them the dexterity to withstand harsh climates. In the present study, we isolated two co-culturable bacterial endophytes, EP1-AS and EP1-BM, from the stem internodal segments of the prostate spurge, Euphorbia prostrata, a plant member of the succulent family Euphorbiaceae. We characterized them using morphological, biochemical, and molecular techniques which revealed them as novel strains of Enterobacteriaceae, Lelliotia amnigena. Both the isolates significantly were qualified during the assaying of their plant growth promotion potentials. BM formed fast-growing swarms while AS showed growth as rounded colonies over nutrient agar. We validated the PGP effects of AS and BM isolates through in vitro and ex vitro seed-priming treatments with wheat and tomato, both of which resulted in significantly enhanced seed germination and morphometric and physiological plant growth profiles. In extended field trials, both AS and BM could remarkably also exhibit productive yields in wheat grain and tomato fruit harvests. This is probably the first-ever study in the context of PGPB endophytes in Euphorbia prostrata. We discuss our results in the context of promising agribiotechnology translations of the endophyte community associated with the otherwise neglected ground-dwelling spurges of Euphorbiaceae.

Chromosome-level Genome Assembly of Euphorbia peplus, a Model System for Plant Latex, Reveals that Relative Lack of Ty3 Transposons Contributed to Its Small Genome Size

Euphorbia peplus (petty spurge) is a small, fast-growing plant that is native to Eurasia and has become a naturalized weed in North America and Australia. Euphorbia peplus is not only medicinally valuable, serving as a source for the skin cancer drug ingenol mebutate, but also has great potential as a model for latex production owing to its small size, ease of manipulation in the laboratory, and rapid reproductive cycle. To help establish E. peplus as a new model, we generated a 267.2-Mb Hi-C-anchored PacBio HiFi nuclear genome assembly with a BUSCO score of 98.5%, a genome annotation based on RNA-seq data from six organs, and publicly accessible tools including a genome browser and an interactive organ-specific expression atlas. Chromosome number is highly variable across Euphorbia species. Using a comparative analysis of our newly sequenced E. peplus genome with other Euphorbiaceae genomes, we show that variation in Euphorbia chromosome number between E. peplus and Euphorbia lathyris is likely due to fragmentation and rearrangement rather than chromosomal duplication followed by diploidization of the duplicated sequence. Moreover, we found that the E. peplus genome is relatively compact compared with related members of the genus in part due to restricted expansion of the Ty3 transposon family. Finally, we identify a large gene cluster that contains many previously identified enzymes in the putative ingenol mebutate biosynthesis pathway, along with additional gene candidates for this biosynthetic pathway. The genomic resources we have created for E. peplus will help advance research on latex production and ingenol mebutate biosynthesis in the commercially important Euphorbiaceae family.