Oyama M, Blumberg D D
Dev Biol. 1986 Oct;117(2):550-6. doi: 10.1016/0012-1606(86)90323-4.
A number of genes encoding developmentally regulated mRNAs in the cellular slime mold, Dictyostelium discoideum, have been described. Many of these are regulated by cAMP. Analysis of the earliest time at which elevated levels of cAMP can induce the expression of these mRNAs reveals a more complex pattern of regulation in which genes change in their ability to be induced in response to cAMP with developmental stage. A prestalk mRNA (C1/D11) previously thought not be regulated by elevated levels of cAMP is inducible by cAMP between aggregation and loose mound stage; later in development its expression becomes independent of elevated cAMP. The early prespore genes (prespore class I) also show two modes of regulation; early in development they are induced independently of continuous elevated levels of cAMP, while later in development their expression is dependent upon elevated cAMP. The period during development when the prestalk genes are cAMP inducible precedes by 2 hr the first time at which either the early prespore class I or late prespore class II mRNAs are inducible by continuous elevated levels of cAMP. Previous analysis of these mRNAs has been carried out using Dictyostelium cells grown axenically. In this report we have studied the developmental expression of these mRNAs in cells grown on bacteria. A substantial shutoff of the class I prestalk and early prespore (class I) mRNAs not seen in axenically grown cells is observed when bacterially grown cells are plated for development. Less than 10% of the maximal level of these mRNAs remains in the cells at the time of mature spore and stalk differentiation. Additionally, in the bacterially grown cells two distinct patterns of developmental regulation are observed for mRNAs which in axenically growing cells appear to be constitutively expressed throughout growth and development.
在细胞黏菌盘基网柄菌中，已描述了许多编码发育调控mRNA的基因。其中许多基因受cAMP调控。对cAMP水平升高可诱导这些mRNA表达的最早时间进行分析，揭示了一种更为复杂的调控模式，即基因响应cAMP的诱导能力随发育阶段而变化。一种先前认为不受cAMP水平升高调控的前柄mRNA（C1/D11）在聚集期和松散丘期之间可被cAMP诱导；在发育后期，其表达变得独立于升高的cAMP。早期前孢子基因（前孢子I类）也表现出两种调控模式；在发育早期，它们的诱导独立于持续升高的cAMP水平，而在发育后期，它们的表达依赖于升高的cAMP。前柄基因可被cAMP诱导的发育时期比早期前孢子I类或晚期前孢子II类mRNA首次被持续升高的cAMP诱导的时间早2小时。此前对这些mRNA的分析是使用无菌培养的盘基网柄菌细胞进行的。在本报告中，我们研究了在细菌上生长的细胞中这些mRNA的发育表达。当将在细菌上生长的细胞接种用于发育时，观察到I类前柄和早期前孢子（I类）mRNA大量关闭，而在无菌培养的细胞中未观察到这种情况。在成熟孢子和柄分化时，这些mRNA的最大水平在细胞中残留不到10%。此外，在细菌上生长的细胞中，对于在无菌生长的细胞中似乎在整个生长和发育过程中组成性表达的mRNA，观察到两种不同的发育调控模式。
