Tuber vegetative stages and cell cycle in Helianthus tuberosus: Protein pattern and their modification by spermidine

This paper reports the protein amount and composition of tuber during its p hases of formation, dormancy and sprouting. Parallely, the break of dormanc y has been induced by excising slices of tuber parenchyma and treating them with 2,4-dichlorophenoxy acetic acid (2,4-D) to induce a new cell cycle; t he protein composition, neosynthesis and post-translational modification by spermidine are reported during the phases of the cell cycle. From tuber fo rmation to sprouting, protein content follows a bimodal trend. The protein bands were separated on sodium dodecyl sulfate polyacrylamide gel electroph oresis and two main bands (38 and 55 kDa) were detected. Many bands, especi ally of high molecular mass, changed their amount during all phases of tube r vegetative period. With the progression of the cell cycle very high molec ular mass proteins increased; neosynthesis and modification by polyamines c ould account for this increase. Parallelly, the amount of lower molecular m ass bands decreased. Many proteins are differently synthesized in the vario us cell cycle phases. Modification by spermidine occurred post-translationa lly, evident by an 18 kDa band (which in fact does not incorporate methioni ne), whose possible identification is discussed. A role for newly synthesiz ed transglutaminases in the protein modification by polyamines is evaluated in the light of the immunodetection of 58 and 90 kDa bands by polyclonal a nti-transglutaminase antibody.