Expressional diversity of wheat nsLTP genes: evidence of subfunctionalization via cis-regulatory divergence

Abstract

Previously, the wheat non-specific lipid transfer proteins (TaLTP), members of a small multigene family, were reported to evidence a complex pattern of expression regulation. In order to assess further the expression diversity of the TaLTP genes, we have attempted to evaluate their expression profiles in responses to abiotic stresses, using semi-quantitative RT-PCR. The expression profiles generated herein revealed that the TaLTP genes in group A evidenced highly similar responses against abiotic stresses, whereas differential expression patterns among genes in each group were also observed. A total of seven promoters were fused to a GUS reporter gene and the recombinants were introduced into Arabidopsis, while three promoters evidenced non-detectible GUS activity. The promoters of TaLTP1, TaLTP7, and TaLTP10 included in group A drove strong expressions during plant development with overlapping patterns, in large part, but also exhibited distinct expression pattern, thereby suggesting subfunctionalization processing over evolutionary time. However, only trace expression in cotyledons, young emerged leaves, and epidermal cell layers of flower ovaries was driven by the promoter of TaLTP3 of group B. These results indicate that their distinct physiological functions appear to be accomplished by a subfunctionalization process involving degenerative mutations in regulatory regions.

Structural genes of wheat and barley 5-methylcytosine DNA glycosylases and their potential applications for human health

“…This might be a consequence of subfunctionalization following polyploidization events that occurred during the evolution of the common wheat from its progenitors. Pseudogenization, concerted evolution, subfunctionalization, or neofunctionalization of ortho(homeo)/paralogous copies of genes in a gene family are commonly reported mechanisms of evolution in polyploids (27)(28)(29)(30).…”

“…This might be a consequence of subfunctionalization following polyploidization events that occurred during the evolution of the common wheat from its progenitors. Pseudogenization, concerted evolution, subfunctionalization, or neofunctionalization of ortho(homeo)/paralogous copies of genes in a gene family are commonly reported mechanisms of evolution in polyploids (27)(28)(29)(30).In summary, these results suggest differential regulation of specific prolamin groups by the different DME homeologs, the expression level of which varies in the individual transformants and also within their progenies, which depend upon the their level of suppression determined by the number and type of siRNAs generated during the processing of double-stranded hairpin (hp)RNA (compare with SI Text). In addition, another layer of complexity arises from the variation in the number and site of integrations and their segregation pattern.…”

Identification of wheat non-specific lipid transfer proteins involved in chilling tolerance

“…Leaves of 10 or more seedlings from the above treatments were harvested at different time points after treatments, frozen immediately in liquid nitrogen, and stored at -80°C. RNA isolation and quantitative RT-PCR (qRT-PCR) were performed as described previously (Wang et al 2010(Wang et al , 2012. The sequence specificity of each amplified band was cloned and confirmed by sequencing.…”

“…None of these members had been functionally identified before. Previous studies of wheat nsLTPs mainly focused on the transcript level, in which a complex expression pattern was shown during the entire life cycle of the plant (Boutrot et al 2008;Wang et al 2010). In this study, we attempted to examine the possible functions and functional redundancies of 3 type I TaLTPs involved in abiotic stresses.…”

Comparative analysis of evolutionary dynamics of genes encoding leucine-rich repeat receptor-like kinase between rice and Arabidopsis

“…For example, some genes duplicated by polyploidy in cotton were reciprocally silenced in different organs, thus supporting the notion of subfunctionalization (Adams et al 2003). Recently, Wang et al (2010) uncovered some evidence suggesting a subfunctionalized process of wheat non-specific lipid transfer protein genes occurring via degenerative mutation in regulatory regions. By way of contrast, a functional buffering hypothesis has been previously proposed involving the preferential retention of duplicated genes on the basis of the vestiges of less radical amino acid changes in genes at paleologous loci than are observed in singleton genes between relatives of Arabidopsis and rice, respectively (Chapman et al 2006).…”