Dysfunction of mitotic cell division at shoot apices triggered severe growth abortion in interspecific hybrids between tetraploid wheat and Aegilops tauschii

Abstract

Summary• Common wheat is an allohexaploid species, derived through endoreduplication of an interspecific triploid hybrid produced from a cross between cultivated tetraploid wheat and the wild diploid relative Aegilops tauschii. Hybrid incompatibilities, including hybrid necrosis, have been observed in triploid wheat hybrids. A limited number of A. tauschii accessions show hybrid lethality in triploid hybrids crossed with tetraploid wheat as a result of developmental arrest at the early seedling stage, which is termed severe growth abortion (SGA). Despite the potential severity of this condition, the genetic mechanisms underlying SGA are not well understood.• Here, we conducted comparative analyses of gene expression profiles in crown tissues to characterize developmental arrest in triploid hybrids displaying SGA.• A number of defense-related genes were highly up-regulated, whereas many transcription factor genes, such as the KNOTTED1-type homeobox gene, which function in shoot apical meristem (SAM) and leaf primordia, were down-regulated in the crown tissues of SGA plants. Transcript accumulation levels of cell cycle-related genes were also markedly reduced in SGA plants, and no histone H4-expressing cells were observed in the SAM of SGA hybrid plants.• Our findings demonstrate that SGA shows unique features among other types of abnormal growth phenotypes, such as type II and III necrosis.

Comparison of gene expression profiles and responses to zinc chloride among inter- and intraspecific hybrids with growth abnormalities in wheat and its relatives

“…Gene expression profiles are not necessarily consistent with each other, but some genes are mutually up-and down-regulated in type II and III necrosis and SGA of ABD triploids (Hatano et al 2012;Mizuno et al 2011). Here, we performed transcriptome analyses for type I and IV necrosis to elucidate the mechanisms inducing necrotic symptoms at the transcriptional level and compared gene expression profiles with those in plants showing growth abnormalities in ABD triploid and synthetic wheat to clarify the common features underlying the various types of hybrid necrosis in Triticum.…”

“…RNA samples were extracted from leaves and crown tissues of synthetic hexaploids after 6 weeks of incubation at 4 °C for plant lines with a type II necrosis phenotype, or with no low-temperature treatment for other plants (Hatano et al 2012;Mizuno et al 2010Mizuno et al , 2011Nakano et al 2015). For the analyses of type II and type III necrosis and hybrid chlorosis, the RNA samples were extracted from leaves starting to appear the abnormal growth symptoms (Mizuno et al 2010Nakano et al 2015).…”

“…Unlike type II and III necrosis and the two types of hybrid chlorosis, severe growth abortion (SGA) is always lethal, because SGA-exhibiting ABD triploids cease development and growth after expansion of the second or third leaves (Mizuno et al 2010;Nishikawa 1960). In spite of their phenotypic difference from type II and III hybrid necrosis, a number of defense-related genes are highly up-regulated in seedlings of SGA-exhibiting hybrids and leaves of synthetic wheat lines with hybrid chlorosis symptoms (Hatano et al 2012;Nakano et al 2015).…”

Association of Wheat miRNAs with Hybrid Incompatibility in Interspecific Crosses of Triticum and Aegilops

“…Severe growth abortion, which is hybrid lethality with developmental arrest at the early seedling stage in ABD wheat hybrids, might be caused by abortion of mitotic cell division and meristematic activity at the SAM (Hatano et al 2012 ). In severe growth abortion, the related cell death induced by an autoimmune response might be a secondary event; arrest of cell division at SAM seems to occur prior to the autoimmune response (Hatano et al 2012 ). Thus, dramatic alteration of gene expression profi les at the SAM induced by the AB and D genome interaction could be signifi cantly associated with the growth abnormalities in triploid wheat hybrids.…”

Comparison of genome-wide gene expression patterns in the seedlings of nascent allohexaploid wheats produced by two combinations of hybrids

“…Most reports used microarray approaches that compare the gene expression levels of the allohexaploids to the averaged level of their parents (Pumphrey et al, 2009;Akhunova et al, 2010;Chagué et al, 2010;Qi et al, 2012;Chelaifa et al, 2013); however, only early generations of allohexaploids were analyzed, and not the F 1 hybrid, i.e., the triploids (ABD), except in one instance (Hatano et al, 2012). The overall gene expression profile of natural allohexaploid wheat reflects the effects of intergenic hybridization, amphidiploidization and genome stabilization during the course of its evolution.…”