期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：23
页码：13560-13565
DOI：10.1073/pnas.96.23.13560
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Phytosulfokine- [PSK-, Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-Gln], a sulfated mitogenic peptide found in plants, strongly promotes proliferation of plant cells in culture at very low concentrations. Oryza sativa PSK (OsPSK) cDNA encoding a PSK- precursor has been isolated. The cDNA is 725 base pairs long, and the 89-aa product, preprophytosulfokine, has a 22-aa hydrophobic region that resembles a cleavable leader peptide at its NH2 terminus. The PSK- sequence occurs only once within the precursor, close to the COOH terminus. [Ser4]PSK- was secreted by transgenic rice Oc cells harboring a mutated OsPSK cDNA, suggesting proteolytic processing from the larger precursor, a feature commonly found in animal systems. Whereas PSK- in conditioned medium with sense transgenic Oc cells was 1.6 times as concentrated as in the control case, antisense transgenic Oc cells produced less than 60% of the control level. Preprophytosulfokine mRNA was detected at an elevated constitutive level in rice Oc culture cells on RNA blot analysis. Although PSK- molecules have never been identified in any intact plant, reverse transcription-PCR analysis demonstrated that OsPSK is expressed in rice seedlings, indicating that PSK- may be important for plant cell proliferation both in vitro and in vivo. DNA blot analysis demonstrated that OsPSK homologs may occur in dicot as well as monocot plants.
