Overexpression of mitochondrial genes is caused by interactions between the nucleus of Brassica rapa and the cytoplasm of Diplotaxis muralis in the leaves of alloplasmic lines of B. rapa

Abstract

In Brassica species, alloplasmic lines displaying cytoplasmic male sterility (CMS) are established by combining the nucleus from B. rapa with the cytoplasm from Diplotaxis muralis. The failure to observe restriction fragment length polymorphism (RFLP) patterns of mitochondrial genes ( coxII, coxIII, atpA, atp6, atp9, cob, nad3, nad6, and nad9) between alloplasmic lines of B. rapa and D. muralis indicates that introgression of the B. rapa nucleus into the cytoplasm of D. muralis does not cause any alterations in the structure of the mitochondrial genome. To investigate how the nucleus influences the cytoplasm, we examined the expression of mitochondrial genes in the leaves of euplasmic and alloplasmic lines of B. rapa and D. muralis. We detected higher levels of mitochondrial gene mRNAs in alloplasmic lines of B. rapa than in D. muralis. Patterns of mitochondrial gene transcription also differed among the alloplasmic lines of B. rapa. Thus, expression of mitochondrial genes in alloplasmic lines of B. rapa differed in the leaves compared to D. muralis. Overexpression of mitochondrial genes may be the result of novel interactions between the nucleus and the mitochondria in alloplasmic lines of B. rapa. Further study is necessary to clarify how these phenomena are involved in CMS.

Mitochondrial atp9 genes from petaloid male-sterile and male-fertile carrots differ in their status of heteroplasmy, recombination involvement, post-transcriptional processing as well as accumulation of RNA and protein product

“…Increased levels of mitochondrial mRNAs have been reported for alloplasmic lines of Brassica rapa carrying the cytoplasm of Diplotaxis muralis (Yamasaki et al 2004). The authors postulate that this enhanced expression results from novel nucleo-mitochondrial interactions.…”

Possibility of a Positive Correlation between the Delay of the Meiosis Stage of Pollen Development and the Degree of Male Sterility among Three Alloplasmic Lines of Brassica rapa Containing Diprotaxis muralis Cytoplasm

“…The characteristics of the plant materials used in the present study have been reported elsewhere (Hinata and Konno, 1979;Yamasaki et al, 1998;Yamasaki et al, 2004). In brief, three euplasmic lines of B. rapa (maintainer lines), its wild relative D. muralis, and three alloplasmic lines of B. rapa were used in the present study (Table 1; Fig.…”

“…In flower buds, additional production of a 2.5-kb coxI transcript and reduced accumulation of nad3 mRNA occur in three alloplasmic lines of B. rapa (MS-Yukina, MS-Kabu, and PMS-Hakusai) vs. D. muralis (Yamasaki et al, 1998). In the leaves, overexpression of atpA, atp6, atp9, cob, coxII, coxIII, and nad6 was detected in MS-Kabu and PMS-Hakusai vs. D. muralis (Yamasaki et al, 2004). However, the differences observed in the degree of male sterility among the three alloplasmic lines of B. rapa could not be attributed to differences in the expression of mitochondrial genes.…”

“…Two alloplasmic lines that show a complete male sterile (MS) phenotype were designated as MS-Yukina and MSKabu, whereas one alloplasmic line that releases some pollen grains was designated as partial male sterile (PMS)-Hakusai (Table 1). The expression of mitochondrial genes in the flower buds and leaves of normal (euplasmic) and alloplasmic lines of B. rapa and D. muralis has previously been examined (Yamasaki et al, 1998;Yamasaki et al, 2004). In flower buds, additional production of a 2.5-kb coxI transcript and reduced accumulation of nad3 mRNA occur in three alloplasmic lines of B. rapa (MS-Yukina, MS-Kabu, and PMS-Hakusai) vs. D. muralis (Yamasaki et al, 1998).…”

Development of two new molecular markers specific to cytoplasmic male sterility in tuber mustard (Brassica juncea var. tumida Tsen et Lee)

“…In more than 300 higher plant species (Liu et al 2001), CMS is caused by the incompatibility between the nucleus and cytoplasm. Moreover, it is often induced by interspecies or inter-generic sexual crosses or asexual protoplast fusion (Yamasaki et al 2004;Liu et al 1996;Hirata et al 2001;Motegi et al 2003). Since CMS was discovered at the beginning of the twentieth century, they have been widely explored and applied for the production of hybrid crop seeds.…”