Plant Science 152 2000 17 – 26
Molecular cloning and characterization of OsLRK1 encoding a putative receptor-like protein kinase from Oryza sati6a
Chanhong Kim, Dong-Hoon Jeong, Gynheung An
Department of Life Science, Pohang Uni6ersity of Science and Technology, Pohang
790
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784
, South Korea Received 13 September 1999; received in revised form 15 September 1999; accepted 16 September 1999
Abstract
A cDNA clone, OsLRK1, encoding a leucine-rich repeat receptor-like protein kinase was isolated from the immature panicles of rice. The OsLRK1 protein was composed of a leucine-rich extracellular ligand-binding domain, a membrane-spanning segment,
and a cytoplasmic kinase domain. The OsLRK1 protein showed the highest sequence homology with Arabidopsis CLV1. The OsLRK1 transcript was present at a high level in immature panicles and at a low level in seedling shoots, immature seeds, and
mature seeds, while no expression was detected in seedling roots and panicles at the heading stage. This expression pattern is similar to that of CLV1, which suggests that the rice clone may play a critical role in meristem development. The function of the
rice OsLRK1 gene was studied by the transgenic approach. Antisense expression of OsLRK1 in rice plants resulted in increased numbers of flower organs, suggesting that the OsLRK1 gene is involved in floral meristem activity. © 2000 Elsevier Science
Ireland Ltd. All rights reserved.
Keywords
:
Antisense; CLAVATA1; Floral meristem; Leucine-rich repeats; Receptor kinase; Rice transformation www.elsevier.comlocateplantsci
1. Introduction
Plant development requires the integration of various signaling pathways that recognize and re-
spond to endogenous and exogenous information. Plants perceive and respond to various stimuli
such as hormones, pathogens, nutrients, light, and stress [1 – 5]. However, the mechanisms by which
plants detect and transduce these signals into their cells are poorly understood. Recent evidence sug-
gests that plants have many different types of transmembrane protein kinases that may function
to transduce extracellular information into the cell [6 – 8]. Some of these plant proteins are called
receptor-like protein kinases RLKs.
RLKs appear to serve as receptors for extracel- lular signals that are involved in processes such as
plant growth, development, and defense. The binding of a signal ligand to an RLK may result in
dimerization and activation, leading to a cellular response [9]. RLKs have been identified from a
number of plants and have been categorized into classes based on various structural motifs found in
their extracellular domains [10]. They contain a cytoplasmic protein kinase domain that is acti-
vated when a ligand binds to the extracellular receptor domain.
Recent studies have placed RLKs within various signaling cascades, including those for pathogen
response, developmental processes, and hormone response [11]. The Arabidopsis CLAVATA CLV1
gene, which encodes such a receptor kinase, is required for normal development of the shoot
apical and floral meristem [1]. In cl61 mutants, extended floral meristem activity results in extra
carpel primordia being initiated inside the gynoe- cium [12]. The enlarged meristems, which have
abnormally large pools of undifferentiated and proliferative cells, give rise to an increased number
of flowers from the inflorescence meristem and floral organs from the floral meristem [1,12].
Corresponding author. Tel.: + 82-562-279-3176; fax: + 82-562- 279-2199.
E-mail address
:
geneanpostech.ac.kr G. An 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 2 1 6 - 2
The characterization of the process from floral meristem formation to floral organ primordia for-
mation is an important part of the analysis of flower development. However, very little is known
about the mechanisms controlling how cell fates are determined in the floral meristem. Cell fate
selections include whether to form an organ pri- mordium, which type of organ to differentiate
into, and when to terminate cell proliferative and organogenic activities. Because cell fate selection
in the inflorescence and floral meristems is likely to be a very complex process, it is also likely that
many genes are involved in this process. Analysis of novel floral regulatory genes will provide new
insights into flower development. Much of the studies have been focused on dicot species. In
order to understand flower development in cereal plant species, we have cloned and characterized a
receptor kinase gene, OsLRK1, from rice
2. Materials and methods
