The C4 photosynthesis pathway was discovered in sugarcane. We identified 24 genes for 7 key enzymes related to the nicotinamide adenine dinucleotide phosphate-malic enzyme
(NADP-ME) C4 pathway. Increased expression of core C4 enzymes played a major role in the evolution of C4 photosynthesis34. Based on gene expression and phylogenetic analysis, 8 genes—SsCA1, SsCA2, SsPEPC1, SsPEPC-k1, SsNADP-MDH2,
SsNADP-ME2, SsPPDK1 and SsPPDK-RP2—were identified as C4-type genes .A tandem duplication of SsNADP-ME2, SsNADP-ME1, also displayed a C4 expression profile similar to that of SsNADP-ME2.But the ortholog of SsNADP-ME1 in
maize, ZmNADP-ME (GRMZM2G122479), displayed non-C4-type expression, suggesting that neofunctionalization of SsNADP-ME1 for C4 in sugarcane occurred after the divergence of maize and tribe Andropogoneae.
Fig.Nicotinamide adenine dinucleotide phosphate-malic enzymetype C4 pathway
Tab.The number of putative carbon fixation genes in S. spontaneum, S. bicolor , Z.mays and O.sativa.
|Gene||S. spontaneum||S. bicolor||Z.mays||O.sativa|
|Carbonic anhydrase (CA)||4||4||3||1|
|Phosphoenolpyrvuate carboxylase (PEPC)||5||5||5||5|
|Phosphoenolpyruvate carboxylase kinase (PEPCK)||3||3||3||3|
|Malate dehydrogenase (MDH)||2||2||1||1|
|Malic enzyme (ME)||5||5||5||4|
|Pyruvate phosphate dikinase (PPDK)||2||2||2||2|
|PPDK regulatory protein (RP)||3||3||2||1|