匍枝根霉和半裸镰刀菌侵染甜瓜果实产生的胞壁降解酶与侵染方式

 匍枝根霉(Rhizopus stolonifer)和半裸镰刀菌(Fusarium semitectum)以不同的机制侵染甜瓜果实。匍枝根霉侵染时,菌丝分泌大量的果胶甲酯酶(PME)、多聚半乳糖醛酸酶(PG)、果胶甲基半乳糖醛酸酶(PMG),迅速消解组织中胶层,引起细胞电解质外渗、质壁分离和软腐。菌丝在胞外和细胞间隙生长,不能穿透细胞壁。半裸镰刀菌侵染甜瓜果实时分泌高活力的果胶甲酯酶、果胶裂解酶类(PML)和纤维素酶(Celulase)而缺少果胶水解酶类,菌丝不能迅速消解中胶层,但以直接穿透细胞壁方式侵染组织细胞。这两种病原对甜瓜不同的致腐方式是由它们不同的外泌胞壁降解酶种类和酶学特性所决定的。

THE CELL WALL DEGRADING ENZYMES AND MODE OF INFECTION OF MELON FRUITS BY RHIZOPUS STOLONIFER (Ehrenb.) VUILL AND FUSARIUM SEMITECTUM BERK ET RAV

Rhizopus stolonifer and Fusarium semitectum have different way of infection of melon fruit.The hyphae of R.stolonifer produces high activities of pectin methyl esterase(PME),pectin methylgala cturonase(PMG) and ploygalacturonase(PG) when infect melon fruits.These enzymes cause fast deformation of middle lamella of fruit tissue,lead the sap leakage,plasmalysis and the soft rot.Its hyphae can only grow between the intercellular space of the melon fissue. F.semitectum produces high activities of pectin esterase,pectin and pectic lyases and cellulase,lacking pectin and pectic hydrolases.Its hyphae can directly penetrate the cell wall of melon fruit tissue and cause Fusarium rot after it infects melon fruit.The way of the different rot of the two pathogens are highly depended upon their different secretory cell wall degrading enzymes.