Expression levels of meristem identity and homeotic genes are modified by nuclear–mitochondrial interactions in alloplasmic male‐sterile lines of Brassica napus

Abstract

SummaryHomeotic conversions of anthers were found in cytoplasmic male sterile (CMS) plants of Brassica napus derived from somatic hybrids of B. napus and Arabidopsis thaliana. CMS line flowers displayed petals reduced in size and width and stamens replaced by carpelloid structures. In order to investigate when these developmental aberrations appeared, flower development was analysed histologically, ultrastructurally and molecularly. Disorganized cell divisions were detected in the floral meristems of the CMS lines at stage 4. As CMS is associated with mitochondrial aberrations, ultrastructural analysis of the mitochondria in the floral meristems was performed. Two mitochondrial populations were found in the CMS lines. One type had disrupted cristae, while the other resembled mitochondria typical of B. napus. Furthermore, expression patterns of genes expressed in particular floral whorls were determined. In spite of the aberrant development of the third whorl organs, BnAP3 was expressed as in B. napus during the first six stages of development. However, the levels of BnPI were reduced. At later developmental stages, the expression of both BnAP3 and BnPI was strongly reduced. Interestingly the expression levels of genes responsible for AP3 and PI activation such as LFY, UFO and ASK1 were higher in the CMS lines, which indicates that activation of B-genes in the CMS lines does not occur as in B. napus. Disrupted and dysfunctional mitochondria seem to be one of the first aberrations manifested in CMS which result in a retrograde influence of the expression levels of genes responsible for the second and third whorl organ differentiation.

Non-radioactive <em>in situ</em> Hybridization Protocol Applicable for Norway Spruce and a Range of Plant Species

“…2A and B). These results are in agreement with previous studies 11,15,16 . Probes directed towards the AP3 homologue in P. abies, DAL13, produced signals in the microsporophylls of P. abies male cones both before and after apical meristem termination ( Fig.…”

Altered expression of wheat AINTEGUMENTA homolog, WANT-1, in pistil and pistil-like transformed stamen of an alloplasmic line with Aegilops crassa cytoplasm

“…P pistils, S stamens, L lodicules, tS transformed stamens, pTs partially transformed stamens resulting in cytoplasmic male sterility (Carlsson et al 2007), and sometimes modifying mitochondrial gene expression (Håkansson and Glimelius 1991;Kitagawa et al 2003). Alloplasmic lines showing pistillody generally exhibit aberrant expression patterns of class B MADS-box genes in the third whorl of flowers, and this failure in class B MADS-box gene expression may directly cause transformation of stamens into pistil-like structures (Murai et al 2002;Linke et al 2003;Hama et al 2004;Teixeira et al 2005;Carlsson et al 2007). Besides the class B MADS-box genes, a large number of nuclear genes are differentially expressed in the flowers of alloplasmic lines exhibiting pistillody, as revealed by microarray analysis (Carlsson et al 2007).…”

“…In many cases of cytoplasmic male sterility, nuclearcytoplasm incompatibility induces abortion of pollen. Homeotic transformation of stamens into pistil-like structures is sometimes observed in alloplasmic lines of carrot, Brassica napus, tobacco, and wheat (Farbos et al 2001;Murai et al 2002;Linke et al 2003;Teixeira et al 2005), a phenomenon called pistillody.…”

Cytoplasmic Male Sterility-Related Protein Kinase, OsNek3, is Regulated Downstream of Mitochondrial Protein Phosphatase 2C, DCW11

“…Upon cytoplasmic substitution, genes related in fl oral organ development are regulated aberrantly in tobacco ( Zubko et al 2001 ), wheat ( Murai et al 2002 ), carrot ( Linke et al 2003 ) and Brassica napus ( Geddy et al 2004, Teixeira et al 2005 ). This phenomenon is reviewed in Zubko (2004) and Fujii and Toriyama (2008) .…”