Plant Science 150 (2000) 29–39 Mitotic B-type cyclins are differentially regulated by phytohormones and during yellow lupine nodule development Joanna Jelen ´ ska a , Joanna Deckert b , Eva Kondorosi c , Andrzej B. Legocki a, * a Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12 /14, 61 -704 Poznan ´ , Poland b Laboratory of Plant Ecophysiology, A. Mickiewicz Uniersity, Niepodlegl  os ´ci 14, 61 -713 Poznan ´ , Poland c Institut des Sciences Ve ´ge ´tales, CNRS, Aenue de la Terrasse, 91198 Gif -sur -Yette, France Received 27 May 1999; received in revised form 29 July 1999; accepted 29 July 1999 Abstract The progression of cell cycle in eukaryotes is controlled by protein complexes composed of p34 protein kinase and cyclin subunits. Recently, we have described four B1 type mitotic cyclin in yellow lupine. The presence of several closely related cyclin genes within the same plant species raised the question about tissue specificity of respective cyclins or their different regulations by plant-specific signals. Therefore, we examined the expression pattern of four B1 cyclins in various lupine tissues, with special emphasis put on developing root nodules. We also studied the effect of phytohormones on the level of respective cyclin mRNAs. As expected, cyclin transcript accumulation was restricted to proliferating tissues. Detailed analysis by reverse transcription-PCR and using primers specific to each cyclin allow to establish that different genes are engaged in cell divisions of various meristematic tissues. All four genes were activated during nodule development, however, the Cyc 3 and Cyc 4 genes mostly at the early stages of nodulation, whereas the Cyc 1 and Cyc 2 genes within the mature nodule organs. The expression of cyclins was regulated differently by plant growth factors. Both auxin and cytokinin induced the Cyc 1 and Cyc 4 genes and their transcript level was also abundant within the root, shoot and floral meristems. The precise localisation of cyclin transcripts by in situ hybridisation revealed that lupine nodule meristem was active during the whole process of nodule development, even in old organs. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Cell cycle; Cyclins; Expression; Lupinus luteus www.elsevier.com/locate/plantsci 1. Introduction Plants, like other higher organisms, develop ow- ing to the processes of cellular division, cell expan- sion and differentiation. The formation of any new organ or tissue of defined structure and func- tion starts with cell proliferation. In contrast to animals, plants grow during their whole lifetime. Their growth is observed mostly within the centers of dividing cells such as shoot and root apical meristems and within the cambium. Moreover, plant cells are totipotent and after differentiation they are capable to re-enter the cell cycle as a result of developmental control or in response to plant-specific signals, such as phytohormones, or external factors like light, wounding, pathogenic or symbiotic interactions. In spite of differences in the development of higher plants and other eu- karyotes, the progression through the cell cycle and the key regulators of cell division are con- served throughout the evolution. Cell cycle is controlled at G1/S and G2/M tran- sition by complexes of cyclin-dependent kinases (CDKs) and their regulatory subunits: cyclins (re- viewed in: [1–4]). Different types of cyclins are expressed at specific stages and regulate transition through respective phases of cell cycle: mitotic cyclins control the entry into mitosis (G2/M) and G1 cyclins control the passage through G1 to S * Corresponding author. E-mail address: legocki@ibch.poznan.pl (A.B. Legocki) 0168-9452/00/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII:S0168-9452(99)00158-2