Azospirillum brasilense Can Modulate Salt Stress in Triticum aestivum via MN052803-LTP Regulation and Phosphatidylcholines Content

Azospirillum brasilense may regulate MN052803-LTP expression and the activity of defensive enzymes in wheat ( Triticum aestivum L.) cultivars to improve salinity tolerance. In a primary experiment, germination indexes of 18 wheat cultivars were measured and Sorkhtokhm and Qods were selected as tolerant and sensitive cultivars to salinity, respectively. Selected cultivars inoculated with A. brasilense (Sp245 produce more ABA and Sp7 as standard strain) and grown-up to five days, then salinity (200 mM NaCl) was applied to seedling via Hoagland’s nutrient solution. The relative expression of MN052803-LTP (authors recorded in the Gen Bank) of roots and shoots was measured at 12, 24, and 48 hours after salinity applied. The results showed that MN052803-LTP expression increased in the order of salinity, inoculation, and inoculation plus salinity. Meanwhile, phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) activity increased in the same order in 12 days-old seedlings. In a similar experiment, 10 mM dithiothreitol (DTT) was used as a reducer and inoculation as a stimulator of MN052803-LTP expression, then the relative expression and phosphatidylcholines (PC) content were measured. Although the MN052803-LTP expression and PC was reduced due to the application of DTT, inoculation eliminates its inhibitory effect. The highest amount of PC was observed in inoculated plants, and the lowest in the plants treated with DTT. Probably, A. brasilense improves salt tolerance of wheat cultivars through MN052803-LTP expression, and PC content via repairing the membrane damages by supplying the membrane phospholipids, such as phosphatidylcholine, and accumulation of antioxidant compounds by activating PAL and TAL via membrane lipid-dependent signaling cascades.