Primavera otoño 2020 (Año LXIII Núms. 122-123) Año LXIV Núm. 124-125 horizontes PRIMAVERA / OTOÑO 2021 PUCPR 66 EVALUATION OF GENES FROM BIOFERTILIZING MICROORGANISMS AND THEIR POTENTIAL FOR PLANT TRANSFORMATION Axel X. Flores Torres Pontifical Catholic University of Puerto Rico Biotechnology Master’s Degree Program Abstract Ethylene is a chemical compound found in plants that negatively impacts growth and overall tolerance to abiotic stress. This review will investigate how enzyme 1-aminocyclopropane- 1-carboxylate, known as ACC deaminase, counteracts ethylene’s effects. The metabolic routes of ethylene and ACC deaminase will be studied. Research of published articles will explain how to identify, isolate, and transform gene encoding for ACC deaminase to be inserted into plants. I will discuss application to different crops around the globe to aid them during extreme climates and to regulate the overexpression of ethylene produced by abiotic stress. Introduction Rhizobium spp. are a genus of microorganisms often used as biofertilizers for their beneficial relationships with plants. These microorganisms provide plants with nutrients, hormones, and defenses through their metabolic routes. In 1934, the scientist Richard Gane discovered that the hydrocarbon ethylene is an important natural plant hormone. Ethylene plays a vital role throughout the plant’s life, stimulating and regulating fruit ripening, flower blooming, leaf shedding, and elongation. Under extended periods of abiotic stress, plant metabolism produces excessive ethylene, reducing its overall growth and health. Abiotic stress from non-living factors harms plants. Drought, salinity, and extreme temperatures are examples of these factors affecting worldwide plant growth and crop yields. The enzyme 1-aminocyclopropane-1- carboxylic acid, commonly known as ACC deaminase, is found in rhizobacteria. It can disrupt the metabolic cycle of ethylene while producing α-ketobutyrate. Scientists discovered this during soil microorganism research in 1978. ACC deaminase has shown signs of promoting plant tolerance to abiotic stress, specifically with tolerance to high salinity content in crop soil, metal-polluted soil such as copper, and chilling temperatures. The genes encoding for ACC deaminase have been isolated from rhizobacteria species, identified as acdS and the regulator gene acdR. During the last 15 years, researchers have developed methods to insert these genes into plants. Their main goal has been to produce genetically modified plants that can autonomously regulate their ethylene levels during high abiotic stress events and produce plants that maintain high crop yield during extreme climate events. This review paper will evaluate ethylene’s function in plants, the impact of abiotic stress in crops, the ethylene regulating enzyme known as ACC deaminase, and the genes that encode for the enzyme. It also will evaluate the viability of isolating this enzyme, the genetic transformation methods with custom-built plasmids, and the insertion of acdS and acdR genes directly into plants. Main analysis ACC deaminase is an enzyme found in several plant-growth-promoting bacteria such as Bacillus, Enterobacter, Pseudomonas, and Streptomyces (Yoolong et al., 2019). This enzyme strengthens the host plant’s natural