Stage specific expression of poly(malic acid)-affiliated genes in the life cycle of Physarum polycephalum. Spherulin 3b and polymalatase.
Polymalic acid is receiving interest as a unique biopolymer of the plasmodia of mycetozoa and recently as a biogenic matrix for the synthesis of devices for drug delivery. The acellular slime mold Physarum polycephalum is characterized by two distinctive growth phases: uninucleated amoebae and multinucleated plasmodia. In adverse conditions, plasmodia reversibly transform into spherules. Only plasmodia synthesize poly(malic acid) (PMLA) and PMLA-hydrolase (polymalatase). We have performed suppression subtractive hybridization (SSH) of cDNA from amoebae and plasmodia to identify plasmodium-specific genes involved in PMLA metabolism. We found cDNA encoding a plasmodium-specific, spherulin 3a-like polypeptide, NKA48 (spherulin 3b), but no evidence for a PMLA-synthetase encoding transcript. Inhibitory RNA (RNAi)-induced knockdown of NKA48-cDNA generated a severe reduction in the level of PMLA suggesting that spherulin 3b functioned in regulating the level of PMLA. Unexpectedly, cDNA of polymalatase was not SSH-selected, suggesting its presence also in amoebae. Quantitative PCR then revealed low levels of mRNA in amoebae, high levels in plasmodia, and also low levels in spherules, in agreement with the expression under transcriptional regulation in these cells.
Pinchai
Nadthanan
N
Institut für Biophysik und Physikalische Biochemie der Universität Regensburg, Germany.
Lee
Bong-Seop
BS
Holler
Eggehard
E
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002265:Carboxylic Ester Hydrolases / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D008293:Malates / Q000378:metabolism*; D008969:Molecular Sequence Data; D016839:Physarum polycephalum / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D011108:Polymers / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics*; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D018076:DNA, Complementary; D016054:DNA, Protozoan; D008293:Malates; D011108:Polymers; D015800:Protozoan Proteins; C121060:poly(malic acid); C108191:spherulin 3a protein, Physarum polycephalum; D002265:Carboxylic Ester Hydrolases; C110918:beta-poly(L-malate) hydrolase