Plant Science 151 2000 93 – 101
Characterization of a periclinal chimera variegated tobacco Nicotiana tabacum L.
Chang-Hyu Bae
a
, Tomoko Abe
a,
, Noriko Nagata
a
, Nobuhisa Fukunishi
b
, Tomoki Matsuyama
a
, Takeshi Nakano
a
, Shigeo Yoshida
a
a
Plant Functions Laboratory, RIKEN Institute of Physical and Chemical Research
,
2
-
1
Hirosawa, Wako, Saitama
351
-
0198
, Japan
b
RI Beam Factory Project Office, RIKEN Institute of Physical and Chemical Research
, Wako
351
-
0198
, Japan Received 12 April 1999; received in revised form 4 October 1999; accepted 5 October 1999
Abstract
A plant isolated from a population of tobacco Nicotiana tabacum L. cv. BY-4 lines, which were generated with a heavy-ion beam, exhibited green and white variegation on its leaves, stems, and calyces. Fluorescence microscopic analysis of white and
green sections of the leaves of the mutant showed an absence of developed chloroplasts in the epidermis and palisade layer. There were undeveloped chloroplasts in one or two layers of spongy parenchyma cells in the green sections of the mutant. In the F
1
generation, the segregation ratio of green to white was 6:1163 and reciprocal crosses showed that the variegation was not maternally inherited. These results suggest that the mutant is a periclinal chimera with a White-White-Green histogenic
composition. The mRNA levels of the photosynthetic genes rbcL and psbA in the green areas were normal, while they were significantly reduced in the white areas. © 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.
Keywords
:
Variegated tobacco; Periclinal chimera; Chloroplast gene www.elsevier.comlocateplantsci
1. Introduction
The classic studies of the non-Mendelian inheri- tance of green – white variegation [1] provided sup-
port for the existence of extra-nuclear DNA. Recent studies have reported that this green – white
variegation is associated with the alteration of chloroplast [2 – 5] or mitochondria [6 – 10] genes.
Periclinal chimeras reveal that all three apical lineages contribute to the leaf primordium in to-
bacco [11 – 13]. The cell lineages in periclinal chimeras are referred to as L1 layer 1, L2 layer
2, and L3 layer 3. L1 contributes exclusively to the epidermis; L2 produces the subepidermal layer
of the mesophyll near the center of the leaf; and L3 gives rise to the middle mesophyll layers in the
center of the leaf blade [13]. These relationships have been established in genetic and histological
studies of tobacco [11], poinsettia, and carnation [14]. Periclinal chimeral tobacco plants can have
G-G-G L1-L2-L3, G-G-W, G-W-W, W-W-W, W-W-G, and G-W-G G, green; W, white histo-
genic types in stable homoplastidic periclinal chimeras [12]. Of these six histogenic types, the
leaf phenotypes and the modes of segregation of types G-W-G and W-W-G leaves are very similar,
except that the epidermis is green or white, respec- tively [12].
Several well-known examples of variegation are inherited maternally [3,4,6 – 8,15,16]. This involves
an inherited nuclear gene system [2,17] with a non-Mendelian inheritance pattern [9,18]. In addi-
tion, various modes of inheritance have been re- ported for the leaf histological patterns seen in
variegated tobacco plants [11 – 13]. For example, type W-W-W only produces white progeny, while
types G-W-G and W-W-G produce very few green progeny by self-pollination.
Corresponding author. Tel.: + 81-48-467-9527; fax: + 81-48-462- 4674.
E-mail address
:
tomoaberiken.go.jp T. Abe 0168-945200 - see front matter © 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.
PII: S 0 1 6 8 - 9 4 5 2 9 9 0 0 2 0 5 - 8
An approach using leaf tissue that has naturally lost the ability to photosynthesize is ideal for
studying the expression and regulation of genes related to photosynthesis [6,19]. Genes that di-
rectly or secondarily affect chloroplast form and function have been identified in variegated mu-
tants [2,3,8,10,16]. Therefore, the variegated areas of mutants are extremely useful for studying alter-
ations of photosynthetic genes [7] and they are an excellent starting point to dissect the poorly under-
stood pathways of communication between the nuclear-cytoplasmic, chloroplast, and mitochon-
drial genetic systems [20,21]. In this study, we present the genetic, histological, and molecular
characteristics of a variegated tobacco phenotype, which is a periclinal chimera that has undeveloped
chloroplasts in some of the leaf mesophyll cell layers.
2. Materials and methods
