Functional implications of gene expression analysis from rice tonoplast intrinsic proteins during seed germination and development
2010
Huh, S.M., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Lee, I.S., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Kim, B.G., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Shin, Y.S., National Institute of Crop Science, RDA, Suwon, Republic of Korea | Lee, G.S., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Kim, D.Y., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Kim, D.H., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Byun, M.O., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea | Yoon, I.S., National Academy of Agricultural Science, RDA, Suwon, Republic of Korea
Rice seed maturation and germination involve drastic changes in water and nutrient transport, in which tonoplast aquaporins may play an important role. In the present study, gene expression profiles of 10 tonoplast intrinsic proteins (TIP) from rice were investigated by RT-PCR during seed development and germination. OsTIP3;1 and OsTIP3;2 were specifically expressed in mature seeds. Their transcript level rapidly decreased after onset of seed germination and gene expression was induced by ABA treatment. In contrast, expression of OsTIP2;1 and OsTIP4;3 was not seed specific as transcripts were found in vegetative tissues as well. Their respective transcript levels decreased at an early stage of seed development, whereas they increased at a later stage of seed germination and elongation of embryonic roots and shoots. When seed germination was inhibited by various stress conditions and ABA, expression of OsTIP2;1 and OsTIP4;3 was completely suppressed. In contrast, the expression level of OsTIP2;2 rapidly increased after seed imbibition and the transcript level was maintained under conditions inhibiting seed germination. These results implicate that tissue specific and developmental transcriptional regulation of OsTIPs in rice seeds depends on their specific function. In addition, OsTIPs can be discriminated by different potential phosphorylation and methylation sites in their protein structures. OsTIP3;1 and OsTIP3;2 possess unique phosphorylation signatures at their N-terminal domain, loop B and loop E, respectively. OsTIP2;1 and OsTIP4;3 have a potential methylation site at their Nterminal domain. This suggests that activity of specific tonoplast aquaporins may be regulated by post-translational modification as well as by transcriptional control.
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