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Developmental studies of cytoplasmic male-sterile Brassica napus lines

Teixeira, Rita (2005). Developmental studies of cytoplasmic male-sterile Brassica napus lines. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2005:8
ISBN 91-576-7007-2
[Doctoral thesis]

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The presence of male sterile plants in the wild gained the attention of breeders to utilize the trait for hybrid seed production in economically important crops. For scientists, cytoplasmic male sterile (CMS) plants are regarded as an excellent tool to study the genetic interactions between mitochondria and nucleus in flower development. CMS plants can be obtained after sexual crosses between different species of the same family or by somatic hybridisations between unrelated species. The Brassica napus CMS lines investigated in this thesis were obtained after protoplast fusion between B. napus cv. Hanna and Arabidopsis thaliana var. Landsberg erecta. After several backcrosses using B. napus as the male parent, the cells of the CMS lines contain the nucleus and the plastids from B. napus while the mitochondria have a rearranged mitochondrial (mt) DNA between the two species. The vegetative and flower development of the two CMS lines was compared with B. napus. The CMS plants showed a reduced seedling growth. This slower growth rate was present throughout the vegetative development of the CMS plants. They also bolted later than B. napus. However, when fully matured they were of the same size as B. napus. The reduced number of stem cells and its smaller size during the first six weeks of growth seems to be the reason for the shorter stature of the CMS plants. Metabolic studies revealed that the CMS plants had an abnormal starch accumulation with a concomitant reduction of sucrose levels when compared to B. napus. The CMS plants are mainly characterized by the presence of carpelloid structures in the third whorl of the flower, replacing the stamens of B. napus, and by petals reduced in size. Histological and ultrastructural studies made of young flower buds showed that the cell division pattern in the putative whorls two and three was altered. Cells in the CMS lines had divided in several directions instead of the typical anticlinal cell division present in the two first layers of the B. napus young flower bud. The same alterations in cell division patterning were also observed in the vegetative meristem of the CMS lines. In both these two meristematic tissues (vegetative and floral), two mitochondrial populations were found in the CMS lines. One population of mitochondria resembled the B. napus ones at the ultrastructural level but were always smaller in size. The other population showed disrupted inner-membrane systems and the density of the matrix was strongly reduced. In accordance with the disrupted mitochondria, flower tissues from the CMS plants displayed reduced levels of ATP in comparison to B. napus. All the homeotic genes and their upstream genes showed the same expression pattern in young flower buds between the three lines until third whorl organs had differentiated. Even though the pattern was similar, the expression levels of the same genes showed differences between the two CMS lines and B. napus. By the time third whorl organs started to differentiate, BnAP3 and BnPI expression levels were strongly reduced while the upstream genes like BnUFO and BnLFY were up-regulated. This up-regulation suggest that the action of BnUFO and BnLFY is interrupted when activating BnAP3 and BnPI that in turn, seems to reflect a feedback up-regulation mechanism by the nucleus. This feedback regulation can be explained by the fact that the nuclear genes in the CMS cells are not mutated. The transcription of nuclear genes coding for non-functional proteins will then be up-regulated. The hypothesis developed in this study relates the reduced levels of ATP in the flower tissues of the CMS lines with the protein degradation of key proteins necessary for correct flower development and cell division.

Authors/Creators:Teixeira, Rita
Title:Developmental studies of cytoplasmic male-sterile Brassica napus lines
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2005
Number of Pages:54
ALLI. Leino, M.*, Teixeira, R.*, Landgren, M. and Glimelius, K. (2003) Brassica napus lines with rearranged Arabidopsis mitochondria display CMS and a range of developmental aberrations. Theor. Appl. Genet. 106: 1156-1163. II. Teixeira, R.T., Knorpp, C. and Glimelius, K. (2005) Modified sucrose, starch and ATP levels in two alloplasmic male-sterile lines of B. napus. J. Exp. Bot. (in press). III. Teixeira, R.T., Farbos, I. and Glimelius, K. (2005) Expression levels of meristem identity and homeotic genes are modified by nuclear-mitochondrial interactions in alloplasmic male-sterile lines of Brassica napus. Plant J. (accepted pending revision) IV. Carlsson, J., Teixeira, R.T., Sundström, J., Lagercrantz, U. and Glimelius, K. (2004) Cytoplasmic male sterility Brassica napus displays altered expression in a diverse range of nuclear genes according to microarray analysis. (Manuscript). * These authors contributed equally
Place of Publication:Uppsala
ISBN for printed version:91-576-7007-2
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F62 Plant physiology - Growth and development
Subjects:Not in use, please see Agris categories
Agrovoc terms:brassica napus, cytoplasmic male sterility, biological development, developmental stages, growth, homeotic genes
Keywords:Brassica napus, cytoplasmic male sterility, hybridization, flower development, homeotic genes
Permanent URL:
ID Code:761
Department:(NL, NJ) > Dept. of Plant Biology and Forest Genetics (until 131231)
Deposited By: rita teixeira
Deposited On:14 Feb 2005 00:00
Metadata Last Modified:02 Dec 2014 10:07

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