White B T, Yanofsky C
Department of Biological Sciences, Stanford University, California 94305.
Dev Biol. 1993 Nov;160(1):254-64. doi: 10.1006/dbio.1993.1303.
The gene con-6 of Neurospora crassa is expressed during the formation of asexual spores (conidia), but it is not expressed in mycelium. con-6 mRNA appears upon induction of conidiation and reaches high levels at the late stages of conidiation, and in mature conidia. The CON6 polypeptide and a CON6-beta-Gal fusion protein were present at high levels only in free conidia. Shortly after spore germination con-6 mRNA disappears and the CON6 polypeptide is degraded. CON6 is a small, hydrophilic polypeptide containing a repeat sequence; it not homologous to any known protein but has features resembling the late embryogenesis abundant proteins of maize. Inactivation of con-6 by the repeat-induced point mutation process had no demonstrable effect on formation or germination of conidia. Upstream sequence comparisons for con-6 and other con genes identified a common potential regulatory sequence, designated CRS-B. DNA mobility shift analyses with cell extracts identified a factor that bound to synthetic DNA fragments containing this sequence. This binding factor was present in mycelium but not in conidiating cultures. Experiments with independent integrated con-6'-'lacZ translational fusions revealed substantial variability of expression among transformants carrying identical fusion constructs: This variability may be due to the differential methylation of transformant DNA noted by others.
粗糙脉孢菌的基因con-6在无性孢子（分生孢子）形成过程中表达，但在菌丝体中不表达。con-6 mRNA在分生孢子形成诱导时出现，并在分生孢子形成后期及成熟分生孢子中达到高水平。CON6多肽和CON6-β-半乳糖苷酶融合蛋白仅在游离分生孢子中高水平存在。孢子萌发后不久，con-6 mRNA消失，CON6多肽被降解。CON6是一种含有重复序列的小亲水性多肽；它与任何已知蛋白质都不同源，但具有类似于玉米晚期胚胎发育丰富蛋白的特征。通过重复诱导点突变过程使con-6失活对分生孢子的形成或萌发没有明显影响。对con-6和其他con基因的上游序列比较确定了一个共同的潜在调控序列，称为CRS-B。用细胞提取物进行的DNA迁移率变动分析确定了一种与含有该序列的合成DNA片段结合的因子。这种结合因子存在于菌丝体中，但不存在于分生孢子形成培养物中。对独立整合的con-6'-'lacZ翻译融合体的实验表明，携带相同融合构建体的转化体之间表达存在很大差异：这种差异可能是由于其他人所指出的转化体DNA的差异甲基化所致。
