Co-ordinate regulation of cytokinin gene family members during flag leaf and reproductive development in wheat

Abstract

BackgroundAs the global population continues to expand, increasing yield in bread wheat is of critical importance as 20% of the world’s food supply is sourced from this cereal. Several recent studies of the molecular basis of grain yield indicate that the cytokinins are a key factor in determining grain yield. In this study, cytokinin gene family members in bread wheat were isolated from four multigene families which regulate cytokinin synthesis and metabolism, the isopentenyl transferases (IPT), cytokinin oxidases (CKX), zeatin O-glucosyltransferases (ZOG), and β-glucosidases (GLU). As bread wheat is hexaploid, each gene family is also likely to be represented on the A, B and D genomes. By using a novel strategy of qRT-PCR with locus-specific primers shared among the three homoeologues of each family member, detailed expression profiles are provided of family members of these multigene families expressed during leaf, spike and seed development.ResultsThe expression patterns of individual members of the IPT, CKX, ZOG, and GLU multigene families in wheat are shown to be tissue- and developmentally-specific. For instance, TaIPT2 and TaCKX1 were the most highly expressed family members during early seed development, with relative expression levels of up to 90- and 900-fold higher, respectively, than those in the lowest expressed samples. The expression of two cis-ZOG genes was sharply increased in older leaves, while an extremely high mRNA level of TaGLU1-1 was detected in young leaves.ConclusionsKey genes with tissue- and developmentally-specific expression have been identified which would be prime targets for genetic manipulation towards yield improvement in bread wheat breeding programmes, utilising TILLING and MAS strategies.

Infection byRhodococcus fasciansmaintains cotyledons as a sink tissue for the pathogen

“…The reference genes were first compared for their expression stability over different cDNA samples from tissues at different growth stages, with three replicates. The geometric mean of four reference genes was calculated according to the method described by Song et al (2012), and its correlation to the target gene was compared with every gene of interest.…”

“…Relative gene expression was calculated based on the method of Pfaffl and Hageleit (2001) and Song et al (2012). Gene expression was determined by comparing the expression of the gene of interest/target gene with the average expression of the four reference genes.…”

“…Due to the fact that all samples could not be run in a single PCR run, an inter-run calibrator was used (Derveaux et al, 2010) which was composed of mixed cDNA from all tissues used in the project. The data analysis was done as described by Song et al (2012). For each reference gene, a correction factor (CF) for each of the cDNA samples was calculated using the Ct value of this cDNA sample divided by the average Ct value of all cDNA samples of the same experiment.…”

Signal transduction during wheat grain development

“…It is well known that plant hormones are involved in seed development (Yang et al 2003a;Song et al 2012). Grain hormone content or exogenous application of hormone is significantly correlated to grain-filling rate by modulating the sink strength of the grains and varies with grain-filling stage (Yang et al 2000a, b;Travaglia et al 2010).…”

The mvp2 mutation affects the generative transition through the modification of transcriptome pattern, salicylic acid and cytokinin metabolism in Triticum monococcum

“…Similarity 16 of the response of cytokinin phosphates in both genotypes might be given by the prevailing 17 effect of low temperature that negatively affects cytokinin biosynthesis and, as a consequence, 18 plant growth rate. 19 The concentration of active cytokinins is controlled at transcriptional level by several 20 multigene families including isopentenyl transferases for synthesis, cytokinin 21 oxidases/dehydrogenases for degradation, trans/cis-zeatin O-glycosyltransferases for 22 reversible inactivation and beta-glucosidases for reactivation (Song et al, 2012). Among 23 them, a gene encoding zeatin O-glycosyltransferase was affected by the mvp2 mutation and 24 corresponding differences were found in cis/trans-zeatin O-glucoside content between wt and 25 mvp2 plants.…”