Arabidopsis 10-formyl tetrahydrofolate deformylases are essential for photorespiration.
In prokaryotes, PurU (10-formyl tetrahydrofolate [THF] deformylase) metabolizes 10-formyl THF to formate and THF for purine and Gly biosyntheses. The Arabidopsis thaliana genome contains two putative purU genes, At4g17360 and At5g47435. Knocking out these genes simultaneously results in plants that are smaller and paler than the wild type. These double knockout (dKO) mutant plants show a 70-fold increase in Gly levels and accumulate elevated levels of 5- and 10-formyl THF. Embryo development in dKO mutants arrests between heart and early bent cotyledon stages. Mature seeds are shriveled, accumulate low amounts of lipids, and fail to germinate. However, the dKO mutant is only conditionally lethal and is rescued by growth under nonphotorespiratory conditions. In addition, culturing dKO siliques in the presence of sucrose restores normal embryo development and seed viability, suggesting that the seed and embryo development phenotypes are a result of a maternal effect. Our findings are consistent with the involvement of At4g17360 and At5g47435 proteins in photorespiration, which is to prevent excessive accumulation of 5-formyl THF, a potent inhibitor of the Gly decarboxylase/Ser hydroxymethyltransferase complex. Supporting this role, deletion of the At2g38660 gene that encodes the bifunctional 5,10-methylene THF dehydrogenase/5,10-methenyl THF cyclohydrolase that acts upstream of 5-formyl THF formation restored the wild-type phenotype in dKO plants.
Collakova
Eva
E
Plant Biology Department, Michigan State University, East Lansing, Michigan 48824, USA. collakov@msu.edu
Goyer
Aymeric
A
Naponelli
Valeria
V
Krassovskaya
Inga
I
Gregory
Jesse F
JF
Hanson
Andrew D
AD
Shachar-Hill
Yair
Y
D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D005492:Folic Acid / Q000378:metabolism; D005561:Formates / Q000378:metabolism; D005575:Formyltetrahydrofolates / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D012696:Glycine Hydroxymethyltransferase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013395:Sucrose / Q000494:pharmacology
D029681:Arabidopsis Proteins; D005561:Formates; D005575:Formyltetrahydrofolates; C030544:formic acid; D013395:Sucrose; D005492:Folic Acid; D012696:Glycine Hydroxymethyltransferase; D000581:Amidohydrolases; C084507:peptide deformylase; D010100:Oxygen