OsACL-A2 is involved in iron transport and positively regulates iron dependent disease resistance

Iron is an essential nutrient required for growth, development and also impacts disease resistance in plants. Plant absorb iron through their roots and citrate plays a vital role in transport of Fe through the xylem. In this study, we found that the rice cytoplasmic ATP-citrate lyase subunit A2, OsACL-A2 ( Os12g0566300 ) serves as a crucial factor in iron uptake and translocation. Leaf iron levels were depressed in the osacl-a2 mutant which caused iron deficiency induced chlorosis, activated defense signaling and eventually necrosis in mature leaves. Furthermore, loss of OsACL-A2 activity reduced disease resistance in leaves that had not reached development of necrosis. Citrate levels are increased in the osacl-a2 mutant, while ACL activity in the wild type is upregulated in response to both iron starvation and pathogen attack. We hypothesize that OsACL-A2 activity generates source-sink gradients through targeted lysis activity thus directing the movement of citrate-Fe .