Figure 2.

Differentially expressed lemon leaf transcripts involved in S-adenosylmethionine (SAM) metabolism identified between CLas and control grafted plants. At 2 weeks post graft (wpg), methionine-γ-lyase (1) transcripts are upregulated in CLas plants, directing flux of methionine toward isoleucine biosynthesis. At 10 wpg, three SAM synthetase (2) transcripts are upregulated in CLas plants, redirecting methionine flux toward production of SAM. A fourth SAM synthetase is upregulated in CLas plants at 14 wpg. ACC oxidase (3) catalyzes ethylene production from SAM, and is upregulated in CLas plants at 10 and 14 wpg. SAM decarboxylase (4), which regulates polyamine biosynthesis from SAM, is upregulated in CLas plants at 14 wpg. Homocysteine methyltransferase (5), cystathionine-β-synthase (6), and adenosine kinase (7) are involved in metabolism of products of the SAM cycle, and are all upregulated in CLas grafted plants 10 wpg. Two SAM-dependent methyltransferases (8) are downregulated in response to CLas, one at 2 wpg and the other at 10 wpg.