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 Uni6ersity, Niepodleglos´ci
14
,
61
-
713
Poznan´, Poland
c
Institut des Sciences Ve´ge´tales, CNRS, A6enue de la Terrasse,
91198
Gif-sur-Y6ette, 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 Cyc3 and Cyc4 genes mostly at the early stages
of nodulation, whereas the Cyc1 and Cyc2 genes within the mature nodule organs. The expression of cyclins was regulated differently by plant growth factors. Both auxin and cytokinin induced the Cyc1 and Cyc4 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.comlocateplantsci
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 G1S and G2M 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 G2M and G1 cyclins control the passage through G1 to S
Corresponding author. E-mail address
:
legockiibch.poznan.pl A.B. Legocki 0168-945200 - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved.
PII: S 0 1 6 8 - 9 4 5 2 9 9 0 0 1 5 8 - 2
phase. Plant cyclins have been recently classified based on their structure and putative function [5].
The nomenclature proposed by Renaudin et al. [5] is used throughout this paper.
Expression of cyclins is restricted to proliferat- ing tissues [6,7] and regulated at multiple levels of
gene expression. Cyclin mRNA and proteins are both unstable molecules and are rapidly degraded
at the end of the respective stages of the cell cycle [8]. Therefore, cyclins are good markers of divid-
ing cells and are used in studies of plant develop- mental processes as well as in search of signaling
pathways leading to the formation of new plant organs.
In our study, we are particularly interested in the regulation of cell-cycle genes during nodule
development in lupine. Symbiotic soil bacteria of the Rhizobiaceae family induce the formation of
nitrogen-fixing nodules on the roots of legume plants. Although many stages of this process were
described in detail reviewed in: [9 – 11], the pre- cise chain of events leading to the appearance of a
new organ still remains to be determined.
We have isolated four clones coding for putative mitotic cyclins of B1 type from Lupinus luteus
nodule cDNA library [12]. Lupine cyclin genes have been named according to the proposed
nomenclature as Luplu;CycB1;1 EMBLGen- Bank accession number U24192, Luplu;CycB
1
;2 U24193,
Luplu;CycB
1
;3 U24194,
Lu- plu;CycB
1
;4 U44857 [12 – 14], but here they are referred as Cyc1, Cyc2, Cyc3 and Cyc4 for sim-
plicity. The presence of a family of closely related cyclins, belonging to the same subgroup, may
suggest their different function during plant devel- opmental processes or their various regulation by
plant-specific factors, such as phytohormones or signals released by symbiotic bacteria. The multi-
ple variants of the same type of plant cell cycle regulators may be necessary to assure flexible reac-
tion to internal signals and variable environment conditions.
In this study we describe a detailed expression pattern of four cyclin genes in various tissues of
lupine, with special emphasis put on developing root nodule and the effect caused by phytohor-
mones. Cyclin expression is analyzed by Northern hybridization, reverse transcription-PCR with the
use of 3-end primers unique to respective cyclin, as well as by in situ hybridization.
2. Materials and methods
