Brassica napus lines with rearranged Arabidopsis mitochondria display CMS and a range of developmental aberrations

Abstract

Numerous Brassica napus (+) Arabidopsis thaliana somatic hybrids were screened for male sterility and aberrant flower phenotypes. Nine hybrids were selected and backcrossed recurrently to B. napus. The resulting lines displayed stable maternal inheritance of flower phenotypes. Nuclear and organellar genomes were characterized molecularly using RFLP analysis. No DNA from A. thaliana was found in the nuclear genome after six back-crosses, whilst the mitochondrial genomes contained rearranged DNA from both A. thaliana and B. napus. Each line tested had a unique RFLP pattern of the mitochondrial DNA (mtDNA) that remained unchanged between the BC(3) and BC(6) generation. The plastid genomes consisted of B. napus DNA. Five lines of the BC(5) generation were subjected to more comprehensive investigations of growth, morphology and fertility. On the basis of these investigations, the five CMS lines could be assigned to two groups, one represented by three lines displaying reduced vegetative development, complete male sterility, and homeotic conversions of stamens into feminized structures. The second group, represented by the other two lines, were not completely male-sterile but still displayed severely affected flower morphologies. These two lines did not display any reduction in vegetative development. For both groups only stamens and petals suffered from the morphological and functional aberrations, while the sepals and pistils displayed normal morphology. All plants were fully female-fertile. Different rearrangements of the mitochondrial genome disturbed nuclear-mitochondrial interactions and led to various types of aberrant growth and flower development. The existence of numerous CMS lines with different mitochondrial patterns involving a species with a sequenced genome offers new opportunities to investigate the genetic regulation of CMS and its associated developmental perturbations.

MADS-Box Genes Are Associated with the Petaloidy/Sepaloidy of Stamens in Cytoplasmic Male Sterile Brassica

“…Similar types of variations were also observed in some Brassica alloplasmic cytoplasm, e.g., the Raphnnus/Ogura (Bannerot et al 1974), species cross B. nigra (L) Koch/B. oleracea L. (Pearson 1972) and B. napus with Arabidopsis cytoplasm (Leino et al 2003). In higher plants, flower development mechanism has been interpreted through the functioning of ABC model, where mutation and over-expression of these genes might lead to homeotic transformations in the flower organization (Zubko 2004).…”

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…The radish Ogura CMS cytoplasm in the B. napus background results in altered floral morphology (Figure 2). Individual cybrid lines containing the B. napus nuclear genome and recombinant mtDNA derived from a combination of B. napus and Arabidopsis exhibited homeotic transformation of anthers to carpels and some disturbances in vegetative growth (Leino et al, 2003). In carrot, lines containing a CMS cytoplasm may exhibit either a petaloid (Figure 2) or a carpeloid phenotype, depending on nuclear background.…”

Modified sucrose, starch, and ATP levels in two alloplasmic male-sterile lines of B. napus

“…Hanna for eight generations resulting in lines with the nuclear genome of B. napus. Southern analysis (Leino et al, 2003) and RFLP analysis (data not shown) demonstrated that the chloroplast genome was of B. napus while the mitochondrial genome had rearranged DNA inherited from B. napus and A. thaliana. Both lines are male sterile and display vegetative aberrations that are stable through successive generations.…”

“…In the present work, two alloplasmic CMS lines of Brassica napus containing rearranged Arabidopsis thaliana mtDNA (Forsberg et al, 1998;Leino et al, 2003) have been investigated and compared to the parental fertile B. napus cultivar. Alloplasmic lines frequently display homeotic conversions that have been attributed to the disturbed interactions between nuclei and mitochondria.…”