Among the biotic factors affecting the production of cassava (Manihot esculenta Crantz), root rot is one of the most severe diseases worldwide. In northern Brazil, the oomycete Phytopythium sp. causes cassava soft root rot disease in the Amazon region. Seeking to understand this plant-pathogen interaction, our main aim was to evaluate changes in expression levels of superoxide dismutase (SOD) and catalase (CAT) genes in susceptible cassava infected by Phytopythium sp., using semi-quantitative RT-PCR assays. Thus, four SOD (three CuZnSOD and one MnSOD) and three CAT genes were selected from the cassava genome available in the Phytozome Database. Comparative sequence analysis revealed high identity between the deduced MeSOD and MeCAT proteins with SODs and CATs from GenBank Database. In addition, putative conserved motifs and metal-binding domains were found within MeCuZnSOD1-3 and MeMnSOD sequences. The deduced MeCAT proteins contain putative domains and conserved motifs, such as a peroxisomal targeting signal. Furthermore, phylogenetic analysis showed that MeCuZnSOD1 and MeCuZnSOD3 proteins were related to SOD [Cu–Zn] 2 (XP_021686055.1) from Hevea brasiliensis, while MeCuZnSOD2 was close to SOD [Cu–Zn] (XP_012089157.1) from Jatropha curcas. MeMnSOD showed a phylogenetic relationship with mitochondrial SOD [Mn] (XP_021684793.1) from H. brasiliensis. The results also revealed phylogenetic proximity of MeCAT2 and MeCAT3 with CAT isozyme 2 (XP_021675148.1), while MeCAT1 was close to CAT isozyme 1 (XP_021675149.1), both from H. brasiliensis. Semi-quantitative RT-PCR assays showed that Phytopythium sp. was able to suppress the expression of MeSOD genes at early stages of infection, while at 48 h after inoculation (HAI) cassava responded by increasing the expression of the MeCuZnSOD3 gene. For the CAT genes, the MeCAT1 gene showed an expression pattern similar to MeCuZnSOD3, while the expression of the MeCAT3 gene was increased at 24 and 48 HAI. The results revealed that cassava responded to Phytopythium sp. infection through changes in transcript levels of different SOD and CAT isoforms, which are known enzymes with crucial functions regarding the oxidative burst produced during plant-pathogen interactions.

在影响木薯（Manihot esculenta Crantz）生产的生物因素中，根腐病是全世界最严重的疾病之一。在巴西北部，卵菌疫霉属（Phytopythium sp。）。在亚马逊地区引起木薯软根腐病。为了了解这种植物-病原体的相互作用，我们的主要目的是评估感染疫霉菌的木薯中超氧化物歧化酶（SOD）和过氧化氢酶（CAT）基因表达水平的变化。使用半定量RT-PCR分析。因此，从Phytozome数据库中的木薯基因组中选择了四个SOD（三个CuZnSOD和一个MnSOD）和三个CAT基因。比较序列分析显示，推断出的MeSOD和MeCAT蛋白与GenBank数据库中的SOD和CAT具有高度同一性。此外，在MeCuZnSOD1-3和MeMnSOD序列中发现了假定的保守基序和金属结合域。推导的MeCAT蛋白包含推定的域和保守的基序，例如过氧化物酶体靶向信号。此外，系统发育分析表明，MeCuZnSOD1和MeCuZnSOD3蛋白与巴西橡胶树的SOD [Cu-Zn] 2（XP_021686055.1）有关，而MeCuZnSOD2与麻疯树的SOD [Cu-Zn]（XP_012089157.1）接近。MeMnSOD与巴西柔丝菌的线粒体SOD [Mn]（XP_021684793.1）表现出亲缘关系。结果还表明，MeCAT2和MeCAT3与CAT同工酶2（XP_021675148.1）的系统发育接近性，而MeCAT1接近于巴西同工杆菌的CAT同工酶1（XP_021675149.1）。半定量RT-PCR测定显示疫霉属。能够在感染的早期抑制MeSOD基因的表达，而在接种（HAI）48小时后，木薯通过增加MeCuZnSOD3基因的表达来应对。对于CAT基因中，MeCAT1基因表现出类似的表达模式MeCuZnSOD3，而表达MeCAT3基因在HAI和24 HAI增加。结果表明，木薯对疫霉菌有反应。通过改变不同SOD和CAT同工型的转录水平来感染细菌，SOD和CAT同工型是已知的酶，对植物与病原体相互作用期间产生的氧化爆发具有关键作用。