Divergent functions of the myotubularin (MTM) homologs AtMTM1 and AtMTM2 in Arabidopsis thaliana: evolution of the plant MTM family.
Myotubularin and myotubularin-related proteins are evolutionarily conserved in eukaryotes. Defects in their function result in muscular dystrophy, neuronal diseases and leukemia in humans. In contrast to the animal lineage, where genes encoding both active and inactive myotubularins (phosphoinositide 3-phosphatases) have appeared and proliferated in the basal metazoan group, myotubularin genes are not found in the unicellular relatives of green plants. However, they are present in land plants encoding proteins highly similar to the active metazoan enzymes. Despite their remarkable structural conservation, plant and animal myotubularins have significantly diverged in their functions. While loss of myotubularin function causes severe disease phenotypes in humans it is not essential for the cellular homeostasis under normal conditions in Arabidopsis thaliana. Instead, myotubularin deficiency is associated with altered tolerance to dehydration stress. The two Arabidopsis genes AtMTM1 and AtMTM2 have originated from a segmental chromosomal duplication and encode catalytically active enzymes. However, only AtMTM1 is involved in elevating the cellular level of phosphatidylinositol 5-phosphate in response to dehydration stress, and the two myotubularins differentially affect the Arabidopsis dehydration stress-responding transcriptome. AtMTM1 and AtMTM2 display different localization patterns in the cell, consistent with the idea that they associate with different membranes to perform specific functions. A single amino acid mutation in AtMTM2 (L250W) results in a dramatic loss of subcellular localization. Mutations in this region are linked to disease conditions in humans.
School of Biological Sciences, University of Nebraska at Lincoln, Lincoln, NE 68588, USA.
Yong
Y
Ding
Ivan
I
Ndamukong
Yang
Y
Zhao
Yuannan
Y
Xia
Jean-Jack
JJ
Riethoven
David R
DR
Jones
Nullin
N
Divecha
Zoya
Z
Avramova
D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D058674:Chromosome Duplication; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism; D003681:Dehydration / Q000378:metabolism; D004789:Enzyme Activation; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012987:Soil; D013312:Stress, Physiological; D059467:Transcriptome
D029681:Arabidopsis Proteins; C524427:MTM1 protein, Arabidopsis; D024101:Mitochondrial Proteins; D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; D012987:Soil; C113567:phosphatidylinositol 5-phosphate; D010744:Phosphoric Monoester Hydrolases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C099588:myotubularin