Abstract
Genetic diversity in cytoplasmic and nuclear genomes and their interaction affecting adaptive traits is an attractive research subject in plants. We addressed submergence stress response of wheat that has become increasingly important but remained largely uninvestigated. Our primary aim was to disclose cytoplasmic diversity using nucleus-cytoplasm (NC) hybrids possessing a series of heterologous cytoplasms in a common nuclear background. Effects of submergence on seedling emergence and growth from imbibed seeds were studied and compared with euplasmic lines. Marked phenotypic variabilities were observed among both lines, demonstrating divergent cytoplasmic and nuclear effects on submergence response. NC hybrids with cytoplasm of Aegilops mutica showed a less inhibition, indicative of their positive contribution to submergence tolerance, whereas cytoplasms of Aegilops umbellulata and related species caused a greater inhibition. Superoxide dismutase (SOD) activity showed a marked increase accompanied by retardation of seedling growth in a susceptible NC hybrid. The observation suggested that the elevated SOD activity was resulted from a high level of reactive oxygen species accumulated and remained in susceptible seedlings. Taken together, our results point to the usefulness of NC hybrids in further studies needed to clarify molecular mechanisms underlying the nucleus-cytoplasm interaction regulating submergence stress response in wheat.
Highlights
Plants possess three interacting and coevolving genomes in three intracellular organelles, i.e. nucleus, mitochondria and chloroplasts
We examined suitability of the bioassay method for evaluation of submergence stress response in wheat using a nuclear donor of standard common wheat cultivar Chinese Spring
Shoot length and total seedling fresh weight continuously increased, whereas root length reached a plateau after 14 days of incubation, indicating that root growth was restricted during the later stages even without submergence stress under our bioassay conditions
Summary
Plants possess three interacting and coevolving genomes in three intracellular organelles, i.e. nucleus, mitochondria and chloroplasts. Studies of interspecific and intergeneric diversity in cytoplasms and nucleus-cytoplasm interactions have been extended to various phenotypes including male-sterility[11,12,13], growth vigor[11], viability[14], inter-crossability and speciation[15,16], photosynthesis and respiration[17,18], transcriptomes and metabolomes[19], and other agronomically important traits[20,21,22] In such studies, hexaploid and tetraploid NC hybrids with cytoplasms of Triticum, Aegilops, Agropyron, Haynaldia and a wild relative of barley Hordeum chilense have been used. We used a series of NC hybrids possessing heterologous cytoplasms derived from the Triticum-Aegilops complex combined with a common nucleus of a paternal donor parent, and compared their response to that of wheat accessions covering a wide range of genetic diversity. We point to the invaluable usefulness of NC hybrids as materials in further studies to elucidate molecular mechanisms underlying nucleus-cytoplasm interactions that regulate submergence stress response in wheat
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