Study About The Mechanism Of Nitrogen Signal Regulating Salinity-Alkalinity Adaption And The Function Of SAMS And GSNOR In Solanum Lycopersicum L.

There are831million hectares of soils affected by excessive salinity-alkalinity in the world, which is nearly arable land area of10percent. Of this,434million hectares are sodic soils (alkaline), compared with397million hectares of saline soils. The response of vegetable crops to saline stress has been extensively studied; however, little literatures emerged about vegetable crops response and adaption to alkali stress in recent years. Tomato (Solanum lycopersicum L.) is one of the most important Solanaceous fruit vegetable crops, which is widely grown in open field as well as greenhouse. In addition, tomato is a moderate salt-tolerance plant, which can be used in vegetable production with new culture technique or genetic engineering in saline-alkali soil. So, understanding the differences between neutral and alkali salt stress on tomato; discovering the mechanism of salinity-alkalinity stress tolerance of tomato; looking for salinity-alkalinity tolerance genes; and discussing the technical measures and theoretical basis for improving tomato salinity-alkalinity tolerance is very important.1Comparative effects of NaCl and NaHCO3stress on physiologiical response in tomato seedlingsWith increasing stress intensity, accumulation of biomass, photosynthesis, chlorophyll contents, respiration, nitrogenous metabolism, absorbing capacity of nutrient were significantly decreased in both NaCl and NaHCO3treatments. However, contents of Na+, ROS and MDA, as well as Na+/K+ratio were significantly increased in both NaCl and NaHCO3treatments with increasing stress intensity. Compared to NaCl stress, NaHCO3stress showed greater chlorosis and oxidative damage on tomato that reduce the biomass accumulation of seedlings. Tartaric acid, oxalic acid and malic acid were accumulated in both NaCl and NaHCO3stress. However, citric acid, butanedioic acid and lactic acid could only be accumulated byNaHCO3treatment in tomato root. The respiratory electron transport pathway shifted from p’Vcyt to pValt in slight NaCl and NaHCO3stress with increased activities of SOD, POD, CAT, APX, DHAR, GR and contents of ASA and GSH, by which tomato seedlings can resist the NaCl and NaHCO3stress-induced ROS injury. High concentrations of NaHCO3inhibited the antioxidative system more seriously than NaCl, especially in root tissues. All together, NaHCO3stress is more serious than NaCl stress with same concentrations, which is based on the excess Na+and high pH stress of NaHCO3stress. Also, organic acids accumulation and enhancing antioxidative system is the main physiological mechanism of tomato seedlings against the NaCl and NaHCO3stress.2Identification of proteins response to NaCl and NaHCO3stress in tomato rootSoil salinity and alkalinity are common constraints to crop productivity in low rainfall regions of the world. However, the physiological difference of plant response to these two stresses was short of deep investigation. This study has identified a set of differentially expressed proteins of tomato root exploring to NaCl and NaHC03stress by iTRAQ (isobaric tags for relative and absolute quantitation) assay. A total of313proteins responsive to NaCl and NaHC03were observed. Among these proteins,70and114proteins were up-regulated by salt and alkali stress, respectively. While down-regulated proteins were80in salt treatment and83in alkali treatment. Only39up-regulated proteins and30down-regulated proteins were shared by salt and alkali stresses. The majority of the down-regulated proteins accounted for metabolism and energy conversion, and the up-regulated proteins were involved in signaling or transport. Compared with salt stress, alkali stress down-regulated proteins related with the respiratory metabolism, fatty acid oxidative metabolism and nitrogenous metabolism of tomato roots, and up-regulated protein with the reactive oxygen species (ROS) scavenging and ion transport. This study provides a novel insight into tomato roots response to salt and alkali stress at a large translation level.3Sodic alkaline stress mitigation by interaction of PAs and NO involve signal transport in tomatoPAs and NO are two kinds of important signal in mediating plant tolerance to abiotic stress. In this study, we observed that both PAs and NO decreased alkaline stress in tomato plants, which may be a result of their role in regulating nutrient balance and ROS, thereby protecting the photosynthetic system from damage. Further investigation indicated that PAs and NO induced accumulation of each other. Furthermore, the function of PAs could be removed by a NO scavenger, cPTIO. On the other hand, application of MGBQ a PAs synthesis inhibitor, did little to abolish the function of NO. To further elucidate the mechanism by which PAs and NO alleviate alkaline stress, the expression of several genes associated with abiotic stress was analyzed by qRT-PCR. NO and PAs significantly upregulated ion transporters such as the plasma membrane Na+/H+antiporter (SlSOS1), vacuolar Na+/H+exchanger (SINHX1and SINHX2), and Na+transporter and signal components including ROS, MAPK, and Ca2+signal pathways, as well as several transcription factors. All of these play important roles in plant adaptation to stress conditions.4Mechanisms ofoverexpressing SlSaMS1on improving alkali stress tolerance in tomatoSAMS is the key enzyme involved in the biosynthesis of SAM, which serves as a common precursor for PAs and ethylene. A SAM synthetase cDNA (SlSAMSl) was introduced into the tomato genome using the Agrobacterium tumefaciens transformation method. Transgenic plants overexpressing SlSAMS1exhibited a significant increase in tolerance to alkali stress and maintained nutrient balance, higher photosynthetic capacity and Lower oxidative stress compared with WT lines. Both in vivo and in vitro experiments indicated that the function of SlSAMS1mainly depended on the accumulation of Spd and Spm in the transgenic lines. A grafting experiment showed that rootstocks from SlSAMS1-overexpressing plants provided a stronger root system, increased PAs accumulation, essential elements absorption, and decreased Na+absorption in the scions under alkali stress. As a result, fruit set and yield were significantly enhanced. To our knowledge, this is the first report to provide evidence that SlSAMSl positively regulates tomato tolerance to alkali stress and plays a major role in modulating polyamine metabolism, resulting in maintainability of nutrient and ROS balance.5Mechanisms of overexpressing SlSAMS1on improving drought and salt stress tolerance in tomatoTransgenic plants overexpressing SlSAMS1exhibited a significant increase in tolerance to drought and salt stress and maintained higher photosynthetic capacity, antioxidative ability and lower water dissipation compared with WT lines. Further study indicated that SlSAMS1is an ABA-response gene, which had effect on amplifying drought-induced ABA signal. In addition, PAO-induced H2O2signal plays an important role in this signal transport. All together, this study indicated that overexpression of SlSAMS1improves drought stress tolerance by ABA-regulated stomatal closure and water dissipation.6Effect of over-and anti-expression of SIGSNOR on alkali stress tolerance in tomato GSNOR is a key enzyme that control homeostasis of endogenesis NO. High activity of GSNOR could reduce NO level and low activity of NO increase NO level. A SIGSNOR was introduced into the tomato genome using the Agrobacterium tumefaciens transformation method. We provide evidence that overexpression of SIGSNOR had effect on improving alkali stress tolerance and antiexpression of SIGSNOR made the transgenic lines more sensitivity to alkali stress than WT lines. All above phenotypes were closed related to ROS metabolism, which indicated that there are close relationship of signal transport between RNS and ROS. Whether RNS and ROS acts as stress response regulator or stress-induced destroyer, which depend on concentrations and homeostasis of endogenesis RNS and ROS in plants.