title: Nitrogen starvation-induced cellular crosstalk of ROS-scavenging antioxidants and phytohormone enhanced the biofuel potential of green microalgaAcutodesmus dimorphus.
abstract: BACKGROUND
  Microalgae accumulate a considerable amount of lipids and carbohydrate under nutrient-deficient conditions, which makes them one of the promising sustainable resources for biofuel production. In the present study, to obtain the biomass with higher lipid and carbohydrate contents, we implemented a short-term nitrogen starvation of 1, 2, and 3 days in a green microalgaAcutodesmus dimorphus. Few recent reports suggest that oxidative stress-tolerant microalgae are highly efficient for biofuel production. To study the role of oxidative stress due to nitrogen deficiency, responses of various stress biomarkers like reactive oxygen species (ROS), cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and non-enzymatic scavengers proline and polyphenols were also evaluated. Further, the endogenous levels of phytohormones abscisic acid (ABA) and indole-3-acetic acid (IAA) were also determined to study their response to nitrogen deficiency.
  
  
  RESULTS
  We observed that nitrogen starvation of 2 days is effective to produce biomass containing 29.92% of lipid (comprising about 75% of neutral lipid) and 34.80% of carbohydrate, which is significantly higher (about 23 and 64%, respectively) than that of the control culture. Among all nitrogen-starved cultures, the accumulations of ROS were lower in 2 days starved culture, which can be linked with the several folds higher activities of SOD and CAT in this culture. The accumulations of proline and total polyphenols were also significantly higher (about 4.7- and 1.7-folds, respectively, than that of the control) in 2 days nitrogen-starved culture. The levels of phytohormones once decreased significantly after 1 day, increased continuously up to 3 days of nitrogen starvation.
  
  
  CONCLUSIONS
  The findings of the present study highlight the interaction of nitrogen starvation-induced oxidative stress with the signaling involved in the growth and development of microalga. The study presents a comprehensive picture of the adaptive mechanisms of the cells from a physiological perspective along with providing the strategy to improve the biofuel potential ofA. dimorphusthrough a short-term nitrogen starvation.
authors.affiliation: Division of Salt & Marine Chemicals, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.|Academy of Scientific & Innovative Research (AcSIR), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.
authors.forename: Kaumeel
authors.initials: K
authors.lastname: Chokshi
authors.affiliation: Division of Salt & Marine Chemicals, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.|Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, 226-8503 Japan.
authors.forename: Imran
authors.initials: I
authors.lastname: Pancha
authors.affiliation: Academy of Scientific & Innovative Research (AcSIR), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.|Division of Plant Omics, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.
authors.forename: Arup
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Division of Salt & Marine Chemicals, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.|Academy of Scientific & Innovative Research (AcSIR), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002 India.
authors.forename: Sandhya
authors.initials: S
authors.lastname: Mishra
keywords: Biofuel; Lipid; Microalgae; Nitrogen starvation; Oxidative stress; Reactive oxygen species; Stress-responsive hormone