Identification of three genes expressed primarily during development in Physarum polycephalum

Abstract

During the life cycle of Physarum polycephalum, uninucleate amoebae develop into multinucleate syncytial plasmodia. These two cell types differ greatly in cellular organisation, behaviour and gene expression. Classical genetic analysis has identified the mating-type gene, matA, as the key gene controlling the initiation of plasmodium development, but nothing is known about the molecular events controlled by matA. In order to identify genes involved in regulating plasmodium formation, we constructed a subtracted cDNA library from cells undergoing development. Three genes that have their highest levels of expression during plasmodium development were identified: redA, redB (regulated in development) and mynD (myosin). Both redA and redB are single-copy genes and are not members of gene families. Although redA has no significant sequence similarities to known genes, redB has sequence similarity to invertebrate sarcoplasmic calcium-binding proteins. The mynD gene is closely related to type II myosin heavy-chain genes from many organisms and is one of a family of type II myosin genes in P. polycephalum. Our results indicate that many more red genes remain to be identified, some of which may play key roles in controlling plasmodium formation.

Transcriptomic changes arising during light-induced sporulation in Physarum polycephalum

“…Assembly and disassembly of actin filaments is controlled by a group of actin-binding proteins, whose activities in turn are regulated by specific signaling pathways. Physarum cell types differ in actin organization but express the same actin genes, suggesting that changes in actin-binding proteins are responsible for the differences in actin organization [28]. Physarum possesses several classes of actin- binding proteins, and most of these proteins display cell type-specific patterns of expression, but their precise roles are not known [29,30].…”

Replicational organization of three weakly expressed loci in Physarum polycephalum

“…The red genes were isolated on the basis of a maximal expression during differentiation of a culture of haploid amoebae into plasmodia (27). No transcripts corresponding to these genes were found in total RNA from amoebae; mRNA levels increased progressively with the percentage of cells committed to differentiate and dropped to a low level in macroplasmodia (28).…”

“…Northern blot analysis indicated that all three genes are maximally expressed during the development of uninucleate amoebae into multinucleate plasmodia; none of the genes are expressed in amoebae and their mRNAs are of low abundance in total RNA from macroplasmodia. The sequences of the cDNA clones do not give any clues to the functions of these genes during development, although redB is related to invertebrate sarcoplasmic calciumbinding proteins (27).…”

“…To determine whether these results are biased by the fact that only abundantly transcribed genes have been studied so far (two actin genes, two histone H4 genes and a profilin gene), we analyze the pattern of replication of three single copy genes transcribed at low levels within the plasmodium (27,28).…”

“…The cDNA clones for the three red genes examined in this study (redA, redB and redE: regulated in development), were isolated from a subtracted cDNA library prepared from developing cultures of P.polycephalum (27,28). Northern blot analysis indicated that all three genes are maximally expressed during the development of uninucleate amoebae into multinucleate plasmodia; none of the genes are expressed in amoebae and their mRNAs are of low abundance in total RNA from macroplasmodia.…”