Functional Analysis Of ACD5 During Infection Of Botrytis Cinerea In Arabidopsis Thaliana

The Arabidopsis ceramide kinase mutant, accelerated cell death 5 (acd5), shows spontaneous cell death in late stage of its development. Compared with the wild-type Arabidopsis thaliana (Col), acd5 is more susceptible to bacterial pathogens in earlier development. Previous studies have shown that ACD5 possesses ceramide kinase (CERK) activity, substrates of CERK will be accumulated to a great extent in acd5 mutant plants, and excessive CERK substrates will lead to plant cell death. However, the mechanism underlying reduced resistance to pathogens caused by ACD5 activity deprivation is still unclear.In this study, we adopted Botrytis cinerea to infect Arabidopsis Col and acd5 mutant plants, and then compared the differences between these two plants, concerning resistance-related signals, plant tissue and cell morphology as well as gene expression which will provide an important information for the future study of the role of ACD5 in the process of plant and pathogen interaction.We found that acd5 mutants exhibit more susceptible to Botrytis cinerea than Col. To be specific, compared with wild type Col, (1) Botrytis cinerea that inoculated on acd5 mutant plants presented a higher germination rate and its hyphal length is also much longer; (2) lesions on acd5 mutant leaves occurred earlier, and disease incidence of acd5 mutant plants is higher ; (3) It is more easily for pathogenic fungi Botrytis cinerea to penetrate epidermis and enter into mesophyll cells of acd5 mutants; (4) The result of trypan blue staining indicates that dead cells induced by pathogens in acd5 mutants appeared much earlier; (5) Signals associated with resistance such as H₂O₂, callose and so on appeared later and less in amount in acd5 mutants than in Col. Meanwhile, expression level of resistance related genes such as PR1, PEROX was lower in acd5 mutants than that in the wild type after inoculation of Botrytis cinerea,. All these data indicate that ACD5 plays a vital role during the process of plants against pathogen infection by regulating the production of plant resistant signals, expression of resistant genes as well as the formation of defensive structures.