Flower development in carrot CMS plants: mitochondria affect the expression of MADS box genes homologous to GLOBOSA and DEFICIENS

Abstract

SummaryMaternally inherited defects in the formation of male¯ower organs leading to cytoplasmic male sterility (CMS) indicate an involvement of mitochondrial genes in the control of¯ower formation. In the`carpeloid' CMS type of carrot, stamens are replaced by carpels. The¯orets thus resemble well-investigated homeotic ower mutants of Arabidopsis and Antirrhinum, in which organ identity is impaired because of the mutation of speci®c nuclear MADS box genes. We have isolated ®ve cDNAs encoding MADS box proteins (DcMADS1±5) from a¯ower-speci®c library of carrot. Structural features deduced from their sequence and transcript patterns in unmodi®ed carrot¯owers determined by in situ hybridisation relate them to known MADS box transcription factors involved in speci®cation of¯ower organs. In`carpeloid' CMS¯ow-ers, we detected a distinctly reduced expression of DcMADS2 and DcMADS3, homologues of the Antirrhinum genes GLOBOSA and DEFICIENS. Our data strongly suggest that the`carpeloid' CMS phenotype is caused by a cytoplasmic (mitochondrial) effect on the expression of two MADS box factors specifying organ development at whorls 2 and 3 of carrot¯owers.

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…In wheat, transcripts of the APETALA3 homolog were reduced in pistilate florets (Murai et al, 2002). In carpeloid carrot flowers, reduced expression of homologs of Antirrhinum GLOBOSA and DEFI-CIENS were detected (Linke et al, 2003). The first direct test of the hypothesis that disturbed expression of the known floral homeotic genes could be responsible for CMS-associated abnormal floral morphology was performed by Bereterbide et al (2002).…”

Plant Mitochondrial Recombination Surveillance Requires Unusual RecA and MutS Homologs

“…In a population of hermaphrodites, male-sterile plants generally have an adaptive advantage due to increased seed production (Charlesworth, 2002), leading to a mating system known as gynodioecy (Darwin, 1877). The CMS phenotype varies widely, from homeotic floral morphological variants (Farbos et al, 2001;Linke et al, 2003) to premature tapetal breakdown (Levings, 1993), incomplete callose deposition (Abad et al, 1995), and gametophytic abortion (Lee et al, 1980). Likewise, the underlying mitochondrial rearrangements associated with CMS are each distinct (Schnable and Wise, 1998).…”

Arabidopsis SHORT INTEGUMENTS 2 Is a Mitochondrial DAR GTPase

“…Complexity in mitochondrial modulation of growth pathways: In plants, mitochondria have been shown to be important for male fertility, appropriate expression of floral homeotic genes, and programmed cell death (Christensen et al 2002;Hoeberichts and Woltering 2003;Leino et al 2003;Linke et al 2003). Work in our laboratory has shown that at least two ribosomal proteins targeted to the mitochondria, HLL and SIN2, are necessary for ovule development and that both also affect the regulation of other developmental pathways in Arabidopsis.…”