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RAF kinase

• Being bold is important on WikipediaPlant ILK1

                Integrin-liked kinsase(ILK) are from the subfamily of Raf-like kinases (RAF). ILKs functions are to interact with the many transmembrane receptors for signaling of different cascades as needed. Little is known so far about ILK’s in plants but intra and extracellular signaling of processes is thought to be the main function at this point. ILK1 has been found in the root system of most plants as well as being co-localized on the plasma membrane as well as the endoplasmic reticulum with the main function being for transport ions across the plasma membrane . ILK1 is known to be responsible for the control of osmotic and salt stress, control of the uptake of nutrients based on availability and pathogen detection .

Potassium levels are found to be of importance when activating flg22, a flagellin peptide comprised of 22 amino acids that triggers pathogen-associated molecular patterns (PAMPs), which functions by activating regulators of bacterial pathogen alert system to notify the cell that cell health has been temporarily compromised. Brauer also found that ion concentration levels of Mn²⁺, Mg²⁺, S and Ca²⁺ were also affected after PAMP detected a bacterial invader of the cell.

ILK1 is part of a very complex whole that is the plant immune system. Aspects of salt stress and nutrient uptake and regulation all work together for the cell to be able to activate other cells that can work to defend the plant from bacterial pathogens. Each of these tasks work together to keep the cell healthy and growing correctly through regulating osmosis, nutrient uptake and pathogen defense which all work together to create a healthy cell. Growth is a necessary factor of plant survival and without a healthy immune system the plant would not be able to survive. 

Osmotic and Salt Stress

ILK1 was found to be linked to hyperosmotic stress sensitivity by Brauer. ILK1 has also been show to help reduce salt stress when seedlings were placed in a solution with increased concentrations of salt. ILK1 levels have been found to remain fairly constant throughout development regardless of high salt exposer. K⁺ homeostasis has also been found to not be affected in high salt concentrations. When increased levels of salt were found in the cell K⁺ levels when ILK1 was present was found to be maintained at the existing level. Previously Aleman found that K⁺ accumulation was reduced in increased salt concentration levels. After a root growth inhibition assay was conducted in an experiment by Brauer that blocked the movement of potassium while not affecting other ions, conclusions were drawn that potassium transport is required for flg22 root growth inhibition and that potassium transport was affected by flg22. 

Nutrient Uptake

                Plants need a variety of nutrients to survive one being K⁺. Potassium is responsible for osmoregulation, membrane potential maintenance, turgor pressure of plant cells which in turn mediates stomata movement and growth of tubules within the plant. Photosynthesis and other metabolic regulations are controlled by potassium.When required K⁺ uptake is not being met for the cell PAMPs are activated to help produce an immune response. There are many pathways involved in this process and all are not known. Calmodulins, specifically CML9, have appeared as important genes to interact with ILK-1 and regulate potassium levels within the cell. While CLM9 primarily regulates Ca²⁺ it is linked to a possible K⁺/Ca²⁺ influx channel.  While interactions are found between CML9 and ILK1, ILK1 Is not a direct phosphorylation target of CML9, autophosphorylation of ILK1 diminished with the addition of CML9 amounts without regard to the amount of calcium available for uptake.

                ILK1 is also affected by Mn²⁺ presence or absence. Auto phosphorylation and substrate phosphorylation activity occurred when exposed to both Mn²⁺ and Mg2^+. Mn²⁺ was found to be dose dependent where Mg²⁺ was not. Specific auto phosphorylation sites were found in the presence of Mn²⁺ but not in the presence of Mg²⁺ which supports the ILK1-dependent phosphorylation suggested above. Mass spectrometry revealed that there were no other kinases present that could have triggered this response.

Pathogen Detection

                ILK1 has been found to promote resistance to bacterial pathogens. ILK is required for flg22 sensitivity in seedlings. Flg22 is a flagellin peptide comprised of 22 amino acids that triggers PAMPS. A dead version of ILK1 was compared with live versions of ILK1 to see the level of resistance when challenged with bacterial pathogens. Brauer et al. found that plants inoculated with dead ILK1 were markedly more susceptible to bacterial infection than live ILK1 suggesting that ILK1 is needed for bacterial pathogen detection. Results of the experiment showed that while ILK1 is used in bacterial pathogen detection it is not used for effect induced defenses.

            Brauer found in another experiment looking at ILK1’s reaction to early PAMP response that ILK1 increases PAMP response and basal immunity through phosphorylation of MPK3 and MPK6 and operates independently to reactive oxygen species (ROS) production. High Affinity Potassium uptake mediators such as HAK5’s have also been found to be integral in the signaling of flg22 . HAK5’s generally work in instances when potassium levels are low. Flg22 has been shown to depolarize the cell’s plasma membrane with HAK5 and ILK1 working together to mediate ion homeostasis to assist with both short and long term actions such as growth and the suppression thereof.