Effect of Some Halotolerant Bacteria and Archaea Applications on Protein Metabolism of Alfalfa Under Different Salinity Conditions
Abstract
Alfalfa is an important forage crop grown widely worldwide. However, its productivity and quality can be significantly affected by various environmental stresses such as high salt levels in the soil (Athar et al, 2022). Salt stress can negatively affect the growth, development and physiology of alfalfa plants, leading to reduced yields and reduced nutritional value (Khan, et al 2019). One of the main metabolic pathways affected by stress in plants is protein metabolism, and alleviating the negative effects of stress factors on protein metabolism through various applications is one of the main strategies to increase plant yield today (Ramadoss et al 2013). In this study, the effects of different halotolerant bacteria (Salicola marasensis, Halobacillus trueperi, Salinicoccus amylolyticus) and different halotolerant archaea (Haloarcula japonica, Halorubrum californiense, Haloterrigena thermotolerans) on protein metabolism of alfalfa grown in the presence of NaCl at different concentrations (0, 50, 100, 200 and 400 mM) added to Hoagland medium were investigated. For this purpose, seedlings grown for 14 days at 25/15oC day/night temperature and 14 hours of natural daylight were collected at the end of the experiment and ground in liquid nitrogen in a mortar. The ground plant samples were then homogenized again by adding 4 times the dry matter PBS-t pH 7.4 with an ultraturrax homogenizer, and total protein level analysis with the BCA method (He, 2011) and protein profile analysis with the SDS-PAGE method (Laemmli, 1970), which are the main methods used to examine changes in protein metabolism in these homogenates, were performed.
While the total protein level of the alfalfa in the control group was determined to be 8.62 g/100 g, it was determined that the total protein amount increased with increasing salt concentration and reached 9.48 g/100 g at 50 mM NaCl concentration, 9.51 g/100 g at 100 mM NaCl concentration, 10.10 g/100 g at 200 mM NaCl concentration and 11.30 g/100 g at 400 mM NaCl concentration.
As a result of SDS-PAGE analysis, 18 individual proteins between 10.3 kDa and 374 kDa were found. Of these individual proteins, the protein with a molecular weight of 25.7 kDa was not expressed at all with salinity, while proteins with a molecular weight of 10.3 and 12.9 kDa were overexpressed. As a result of SDS-PAGE analysis, it was determined that general protein synthesis was suppressed with salinity, but overexpression of the 10.3 kDa protein increased the total protein concentration. As a result, when the total protein amount and protein profile were evaluated together, it was determined that all bacterial and archaeal applications used in the experiment could alleviate the negative effects of salt stress on alfalfa seedlings. However, at 50 mM salt concentration, Salicola marasensis, Halobacillus trueperi, Haloarcula japonica; at 100 mM salt concentration, Salicola marasensis, Halobacillus trueperi, Haloarcula japonica, Halorubrum californiense; At 200-400 mM salt concentration, Salicola marasensis, Halobacillus trueperi, Haloarcula japonica were found to be the most effective in reducing stress. These findings suggest that halotolerant bacteria or archaea applications may be a promising approach to reduce the negative effects of salinity on alfalfa production.
