Microbial Volatile Organic Compound Enhances Arabidopsis Growth through Activation of Nitrate and Ammonium Transport

Microbial volatile organic compounds (mVOCs) play a crucial role in regulating plant growth through plant-microbe indirect interactions. In this study, we have investigated the molecular mechanisms of plant growth promotion by mVOCs released from Acinetobacter sp. WCHAc060042, Cereibacter sphaeroides TS, Pseudomonas putida YH-2, Acinetobacter tjernbergiae DSM 14971, and Pseudomonas sp. CA10. The volatiles, 2,5-dimethylpyrazine (2,5-D) and diethylene glycol (DG), increased the shoot and root dry weight by increasing the chlorophyll (Chl) a, b, total Chl a+b, and carotenoid concentration, and potassium concentration in the shoots of Arabidopsis seedlings at 100 µM. Furthermore, 2,5-D significantly increased the accumulation of total nitrogen, nitrate, and calcium in the shoots as well as ammonium in the roots, whereas the expression of AtNRTs and AtAMTs was highly induced in the roots of Arabidopsis seedlings. The transcriptome profile revealed that 1,753 and 2,766 genes were differentially expressed in the shoots and roots of Arabidopsis, respectively. These genes encompassed plant hormone-related genes, such as SAURs and NRT2 family proteins, as well as defense-related transcription factors, including CNGCs, MAPK cascade, and WRKYs. In conclusion, these results suggest that 2,5-D is a potential candidate for promoting plant growth by regulating nitrate and ammonium transporters.