Tracing Evolutionary and Developmental Implications of Mitochondrial Stoichiometric Shifting in the Common Bean

Abstract

The recombination and copy number shifting activities of the plant mitochondrial genome are widely documented across plant genera, but these genome processes have not been as well examined with regard to their roles in plant evolution. Because of the extensive plant collections of Phaseolus spp and the degree to which cytoplasmic male sterility (cms) has been characterized in the common bean, this system would be valuable for investigating mitochondrial genome dynamics in natural populations. We have used the cms-associated sequence pvs-orf239 as a mitochondrial genetic marker for these studies and have demonstrated its universal presence throughout a diversity of undomesticated Phaseolus lines. Within these populations, the pvs-orf239 sequence is present in high copy number in ∼10% of the lines, but substoichiometric in all others. This mitochondrial sequence, derived apparently by at least two recombination events, is well conserved with two point mutations identified that are both apparently silent with regard to the sterility phenotype. A putative progenitor sequence was identified in Phaseolus glabelus in substoichiometric levels, suggesting that the present-day pvs-orf239 sequence was likely introduced substoichiometrically. Copy number shifting within the mitochondrial genome results in a 1000- to 2000-fold change, so that substoichiometric forms are estimated at less than one copy per every 100 cells. On the basis of PCR analysis of root tips, we postulate that a mitochondrial “transmitted form” resides within the meristem to assure transmission of a complete genetic complement to progeny.

Ethephon Elicits Protection Against Erysiphe necator in Grapevine

“…To check the specificity of the PCR product, melting curves were analyzed for each data point. Transcript levels were calculated as described by Arrieta-Montiel et al (19) using the standard curve method from triplicate data, with actin gene as the internal control and control leaves (at time zero) as the reference sample.…”

Methyl Jasmonate Induces Defense Responses in Grapevine and Triggers Protection against Erysiphe necator

“…To check the specificity of the PCR product, melting curves were analyzed for each data point. Transcript levels were calculated as described by Arrieta-Montiel et al (20) using the standard curve method from triplicate data, with actin gene as internal control and control leaves (at time zero) as reference sample.…”

Break-induced replication is the primary recombination pathway in plant somatic hybrid mitochondria: a model for mt-HGT

“…Furthermore, it is possible to analyze a diverse population of mitogenomes from leaves and calli of a single somatic hybrid line that encompass a wide collection of chimeric molecules present in different cells. This is a great advantage of this approach because molecules with alternative configurations as a result of low frequency recombination events are often at low stoichiometries in plant mitochondria, even with less than one copy per cell and are prone to be lost during plant development (Arrieta-Montiel et al ., 2001; Woloszynska and Trojanowski, 2009). This explains why the somatic hybrid ntpoA01 exhibits a higher number of interparental recombination events (117) than those observed in leaves of the cybrid plants nthn (∼50, Fig.…”