Putative scheme of SAM supply for MAs synthesis and expression changes in the involved genes. A) Biosynthetic pathway of the Met cycle and its collaborative pathways. Enzymes are shown in bold. MTA, methylthioadenosine; MTR, methylthioribose; MTR-1-P, methylthioribose-1-phosphate; MTRu-1-P, methylthioribulose-1-phosphate; KMTP, 1,2-dihydroxy-3-keto-5-methylthiopentene; KMTB, 2-keto-4-methylthiobutyrate; PRPP, phosphoribosyl pyrophosphate; SAMS, SAM synthetase; MTN, methylthioadenosine nucleosidase; MTK, methylthioribose kinase; IDI1, acireductone dioxygenase; IDI2, methylthioriburose-1-phosphate isomerase; DEP, dehydrase-enolase-phosphatase; IDI4, aspartate/tyrosine/aromatic aminotransferase; APRT, adenine phosphoribosyltransferase; PRPPS, PRPP synthetase; RPI, ribose 5-phosphate isomerase; FDH, formate dehydrogenase. B) Expression changes of Met cycle-related genes.