does colour in maize is coded by maternal mitochondrial gene?
Answers
Explanation:
The P2 line of maize (Zea mays) is characterized by mitochondrial genome destabilization, initiated by recessive nuclear mutations. These alleles alter copy number control of mitochondrial subgenomes and disrupt normal transfer of mitochondrial genomic components to progeny, resulting in differences in mitochondrial DNA profiles among sibling plants and between parents and progeny. The mitochondrial DNA changes are often associated with variably defective phenotypes, reflecting depletion of essential mitochondrial genes. The P2 nuclear genotype can be considered a natural mutagenesis system for maize mitochondria. It dramatically accelerates mitochondrial genomic divergence by increasing low copy-number subgenomes, by rapidly amplifying aberrant recombination products, and by causing the random loss of normal components of the mitochondrial genomes.
Plants contain two cytoplasmic genetic systems, chloroplastic and mitochondrial, that function semiautonomously but are regulated by the nuclear genome. Plant mitochondrial genomes are much larger and more complex than are animal and fungal mitochondrial genomes (Palmer, 1990; Wolstenholme and Fauron, 1995). Plant mitochondria contain active recombination systems mediated by relatively large repeated sequences (Palmer and Shields, 1984; Fauron et al., 1995). This type of recombination appears to generate a number of subgenomic mitochondrial DNA (mtDNA) molecules, although a unicircular linkage map can be constructed for most plant mitochondrial genotypes. In addition to this reciprocal recombination that is constantly active during the plant life cycle, a second type of recombination occurs in higher plant mitochondria: rare, irreversible recombination across short (6- to less than 100-bp) repeats that can generate new mtDNA arrangements. On a generational time scale, plant mitochondrial genomic patterns appear to be quite stable, despite the active reciprocal recombination that maintains a multipartite structure of the mitochondrial genome. Currently, little is known about the mechanisms involved in nuclear control of mitochondrial genome stability and subgenome partitioning in plant mitochondria.
Spontaneous plant mitochondrial deletion mutants generated by irreversible recombination have been described in several cases. The nonchromosomal stripe (NCS) mutants of maize (Zea mays; Newton and Coe, 1986) contain deletions in essential genes, including nad4, cox2, and rps3/rpl16 (Newton et al., 1990; Hunt and Newton, 1991; Marienfeld and Newton, 1994; Newton et al., 2004). Each defect severely reduces plant growth, and plants are usually heteroplasmic, i.e. defective plants carry variable ratios of normal versus mutant mtDNAs. Large mtDNA deletions that remove the nad7 gene have been found in Nicotiana sylvestris (Li et al., 1988; Pla et al., 1995). Another example of plant mitochondrial deletions is cytoplasmic reversion to fertility from cytoplasmic male sterility (CMS; Schardl et al., 1985; Newton et al., 1996; Bellaoui et al., 1998; Newton et al., 2004), where usually only CMS-specific mtDNA regions are disrupted. Mitochondrial DNA deletion events are rare. They generate novel but stable mitochondrial genotypes. In most nuclear backgrounds, plant mtDNA restriction digestion patterns have been shown to be unchanged for many generations (e.g. Oro et al., 1985).
There are a growing number of examples of specific nuclear effects on particular components of plant mitochondrial genomes. The most well studied are the Phaseolus vulgaris Fr gene, whose dominant allele drastically reduces the copy number of a single mitochondrial subgenome that confers male sterility (Janska and Mackenzie, 1993; He et al., 1995; Janska et al., 1998), and the chm mutation in Arabidopsis (Arabidopsis thaliana), which causes accumulation of characteristic rearrangements in mtDNA leading to maternally conferred leaf variegation and distortion (Martinez-Zapater et al., 1992; Sakamoto et al., 1996).
Here, we report a novel genetic system in maize characterized by highly destabilized mitochondrial genomes. The P2 line was derived from a South American strain of popcorn and was first described as having maternally transmitted abnormalities, such as poor plant growth and pale streaks on leaves (Brown and Duvick, 1958). We have found that mtDNA from plants in the P2 pedigree accumulate numerous rearrangements with surprising differences between sibling plants. We show that introducing P2-line genes through the male can induce dramatic changes in mtDNA structure and create novel genotypes; thus, the P2 line is a natural mitochondrial mutagenic system in maize.
Hope this is helpful for you !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
HOPE IT'S HELPS YOU.
![](https://hi-static.z-dn.net/files/ded/b96e94c69f8dad8603f0189a4d08ece5.jpg)