Alloplasmic wheats with Aegilops crassa cytoplasm which express photoperiod-sensitive homeotic transformations of anthers, show alterations in mitochondrial DNA structure and transcription

Abstract

Alloplasmic wheat, Triticum aestivum cv. Norin 26, with Aegilops crassa cytoplasm, shows photoperiod-sensitive cytoplasmic male sterility (PCMS). This alloplasmic line expresses pistillody of anthers only when grown in long-day conditions (>15 h light). To assess the molecular basis of the PCMS, we carried out Southern and Northern hybridization analyses on mitochondrial DNAs and RNAs isolated from seedlings of alloplasmic lines showing various PCMS phenotypes using probes for twelve mitochondrial genes. All RFLP patterns of mitochondrial DNA from alloplasmic lines greatly differed from those of common wheat, and were slightly changed from those of the parental species, i.e., Ae. crassa. This indicates that nuclear substitutions between related plant species induce structural alterations in the mitochondrial genome. Furthermore, RFLP patterns of (cr)-N61 and FR-mutant probed with coxIII and orf25 were identical with each other, but different from those of the other alloplasmic lines, indicating that the nuclei of N61 and FR-mutant harbor some gene(s) that induces structural alterations of the mitochondrial genome in the coxIII and orf25 regions. The transcription patterns of atp6 and cob in Ae. crassa type were different from those of T. aestivum type. Furthermore, the orf25 transcript in alloplasmic wheats was about 300 nucleotides longer than that of euplasmic lines, including the Ae. crassa pure line, suggesting that transcription patterns of orf25 are associated with recovery from the PCMS phenomenon. These data clearly show the mutual cross-talk between the nuclear genome and chondriome. These observations raise the possibility that the dysfunction of mitochondria caused by the failure of a cooperative control of mitochondrial gene(s) expression influences the pathway of flower morphogenesis, especially in the process that determines organ identity.