The role of a receptor-like protein kinase (At-RLK3) in the perception of chemical activators in Arabidopsis thaliana

[摘要] English: The involvement of a receptor-like protein kinase, At-RLK3 in the response of A.thaliana to four different plant activators was analyzed in this study. Theactivators were salicylic acid (SA), benzothiadiazole (8TH), acetylsalicylic acid(ASA) and 2,6-dichloroisonicotinic acid (INA). The activation of the defenseresponse was determined measuring both the activity and expression on proteinlevel of β-1,3-glucanases. SA, ASA, 8TH and INA treatments showed an earlytransient induction of β-1,3-glucanase activity after treatment. On protein levelthe majority of polypeptides were constitutively expressed in the SA, 8TH, ASAand INA treated plants, indicating that a pool of inactive β -1,3-glucanase proteinsalready present in the cells, were activated upon treatment. It was only in the SAand 8TH treated plants that newly synthesized polypeptides were visible duringthe later stages of the time studies.Once the activation of β-1,3-glucanases was established, the possibleinvolvement of At-RLK3 in the activation of plant defense mechanisms by plantactivators, was investigated. It was found that At-RLK3 mRNA accumulatedrapidly within plants treated with SA, 8TH, ASA and INA. The results indicated acorrelation between the onset of SAR in the plant and the expression of the At-RLK3 gene.Hydrogen peroxide acts as an early marker for the activation of defenses. Thefact that H202 levels rose after At-RLK3 expression was already induced, led usto suggest that H202 did not act as the primary signal that binds to At-RLK3 butthat it acts downstream of At-RLK3. All four treatments did however show thecharacteristic oxygen burst shortly after application. These results however needto be substantiated by repeating each experiment.In addition to being involved in defense signalling, a role for At-RLK3 in plantdevelopment was also suggested. It was found that the transfer of a second At-RLK3 gene to wild-type plants inhibited the expression of the native gene. Theselower At-RLK3 levels led to an altered phenotype of the transgenic plant,implicating a possible role for At-RLK3 in the development of the plant.Elevated levels of At-RLK3 in transgenic plants led a higher induction of PR-2expression after treatment with salicylic acid. A potential application for At-RLK3in important crops when treated with plant activators could be envisaged.

[发布机构] University of the Free State