A novel heat stress-responsive gene in the marine diatom Chaetoceros compressum encoding two types of transcripts, a trypsin-like protease and its related protein, by alternative RNA splicing.
We investigated the change of mRNA expression patterns in the laboratory-grown diatom Chaetoceros compressum under heat-stress conditions by mRNA arbitrarily primed (RAP) RT-PCR. Cells grown at 20 degrees C were subjected to heat treatment at 30 degrees C for 15 min and subsequently maintained at 20 degrees C for 8 h. Four genes including HI-5 were detected as heat stress-responsive genes by fingerprint analysis of RAP RT-PCR. Cloning for full-length cDNA sequences of HI-5 transcripts and related genomic DNA analysis revealed that two types of mRNA, HI-5a and HI-5b, were transcribed from the single HI-5 gene. While the HI-5a protein contained a catalytic domain characteristic to trypsin-like proteases, the HI-5b protein lacked this domain due to an insertion in the associated mRNA of 112 nucleotides; this insertion sequence contained a stop codon near the central region. Quantitative RT-PCR was performed to investigate the changes in expression levels of the two types of mRNA following heat treatment. The HI-5b transcripts were constitutively expressed in both unstressed and heat-stressed cells. In contrast, the number of HI-5a transcripts markedly increased in cells immediately after heat stress, reaching levels 19-fold higher at 8 h after heat stress than that in unstressed cells. These results suggest that RNA splicing plays a key role in heat stress-dependent expression of the HI-5a and HI-5b transcripts from the single HI-5 gene in the diatom.
Kinoshita
S
S
Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan.
Kaneko
G
G
Lee
J H
JH
Kikuchi
K
K
Yamada
H
H
Hara
T
T
Itoh
Y
Y
Watabe
S
S
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D002470:Cell Survival; D017377:Diatoms / Q000201:enzymology*; D015870:Gene Expression; D018882:Heat Stress Disorders / Q000235:genetics*; D008386:Marine Biology; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; C114880:trypsin-like serine protease; D012697:Serine Endopeptidases