The barley sdw1/denso gene not only controls plant height but also yield and quality. The sdw1/denso gene was mapped to the long arm of chromosome 3H. Comparative genomic analysis revealed that the sdw1/denso gene was located in the syntenic region of the rice semidwarf gene sd1 on chromosome 1. The sd1 gene encodes a gibberellic acid (GA)-20 oxidase enzyme. The gene ortholog of rice sd1 was isolated from barley using polymerase chain reaction. The barley and rice genes showed a similar gene structure consisting of three exons and two introns. Both genes share 88.3% genomic sequence similarity and 89% amino acid sequence identity. A single nucleotide polymorphism was identified in intron 2 between barley varieties Baudin and AC Metcalfe with Baudin known to contain the denso semidwarf gene. The single nucleotide polymorphism (SNP) marker was mapped to chromosome 3H in a doubled haploid population of Baudin × AC Metcalfe with 178 DH lines. Quantitative trait locus analysis revealed that plant height cosegregated with the SNP. The sdw1/denso gene in barley is the most likely ortholog of the sd1 in rice. The result will facilitate understanding of the molecular mechanism controlling semidwarf phenotype and provide a diagnostic marker for selection of semidwarf gene in barley. Electronic supplementary materialThe online version of this article

These two authors contributed equally to this work. SummaryWe generated T-DNA insertions throughout the rice genome for saturation mutagenesis. More than 1000 anking sequences were mapped on 12 rice chromosomes. Our results showed that T-DNA tags were not randomly spread on rice chromosomes and were preferentially inserted in gene-rich regions. Few insertions (2.4%) were found in repetitive regions. T-DNA insertions in genic (58.1%) and intergenic regions (41.9%) showed a good correlation with the predicted size distribution of these sequences in the rice genome. Whereas, obvious biases were found for the insertions in the 5 H -and 3 H -regulatory regions outside the coding regions both at 500-bp size and in introns rather than in exons. Such distribution patterns and biases for T-DNA integration in rice are similar to that of the previous report in Arabidopsis, which may result from T-DNA integration mechanism itself. Rice will require approximately the same number of T-DNA insertions for saturation mutagenesis as will Arabidopsis. A database of the T-DNA insertion sites in rice is publicly available at our web site (http://www.genomics.zju.edu.cn/ricetdna).

Two genes with a common region that is characteristic of the TPSI1/Mt4 family were cloned from a Pi-starvationinduced cDNA library of rice roots using suppression subtracted hybridization (SSH). Based on the consensus sequence of these two genes, members of the TPSI1/Mt4 family were found in maize, wheat and barley. BLAST and a cluster analysis in the eight members of the TPSI1/Mt4 family showed two classes of four genes each among monocots. The first gene from rice was designated OsIPS1 based on a comparison of the consensus sequence with AtIPS1 , and consequently the second gene, which has been previously reported as OsPI1 , was designated OsIPS2 . Accumulation of the mRNA of OsIPS1/2 was examined by northern blotting and quantitative reverse transcriptasepolymerase chain reaction in whole-root and split-root experiments under treatment with phosphate (Pi) and the Pi analogue phosphite (Phi). OsIPS1 showed much higher mRNA accumulation in roots than OsIPS2 , and an opposite trend was seen in shoots. OsIPS1/2 showed both systemic and local responses to Pi starvation, and less than 10% of the overall induced mRNA level was due to the local Pi concentration in roots. The results indicate that Phi may interfere with earlier events in roots that are associated with a local Pi signalling pathway. An analysis of transgenic plants showed that OsIPS1/2 are independently responsive to Pi signalling and are mainly expressed in lateral roots and in the vascular cylinder in the primary root. Exogenous cytokinin (6-BA) almost completely suppressed systemic Pi starvation signalling and partially suppressed local Pi signalling. Exogenous abscisic acid remarkably reduced Pi starvation signalling. In contrast, exogenous auxin enhanced Pi signalling, especially local Pi signalling in roots. Exogenous ethylene (ethyphon) and the ratio of auxin to cytokinins did not appear to affect the expression of these two genes.

The plant gaseous hormone ethylene regulates many aspects of plant growth, development and responses to the environment. ETHYLENE INSENSITIVE3 (EIN3) is a transcription factor involved in the ethylene signal transduction pathway in Arabidopsis. To gain a better understanding of the ethylene signal transduction pathway in rice, six EIN3-like genes (designated OsEIL1-6) were identified. OsEIL1, which showed highest similarity with EIN3, was isolated and functionally characterized. Ectopic expression of OsEIL1 in Arabidopsis can partially complement the ein3-1 mutant. The transgenic rice plants with overexpression of OsEIL1 exhibit short root, coiled primary root and slightly short shoot phenotype and elevated response to exogenous ethylene. OsEBP89, an ethylene responsive element binding protein (EREBP) and OsACO1, an ACC (1-aminocyclopropane-1-carboxylic acid) oxidase gene were enhanced in the OsEIL1 overexpressing transgenic plants. These results indicate that OsEIL1 is involved in ethylene signal transduction pathway and acts as a positive regulator of ethylene response in rice.

BackgroundThe dwarfing gene sdw1 has been widely used throughout the world to develop commercial barley varieties. There are at least four different alleles at the sdw1 locus.ResultsMutations in the gibberellin 20-oxidase gene (HvGA20ox2) resulted in multiple alleles at the sdw1 locus. The sdw1.d allele from Diamant is due to a 7-bp deletion in exon 1, while the sdw1.c allele from Abed Denso has 1-bp deletion and a 4-bp insertion in the 5’ untranslated region. The sdw1.a allele from Jotun resulted from a total deletion of the HvGA20ox2 gene. The structural changes result in lower gene expression in sdw1.d and lack of expression in sdw1.a. There are three HvGA20ox genes in the barley genome. The partial or total loss of function of the HvGA20ox2 gene could be compensated by enhanced expression of its homolog HvGA20ox1and HvGA20ox3. A diagnostic molecular marker was developed to differentiate between the wild-type, sdw1.d and sdw1.a alleles and another molecular marker for differentiation of sdw1.c and sdw1.a. The markers were further tested in 197 barley varieties, out of which 28 had the sdw1.d allele and two varieties the sdw1.a allele. To date, the sdw1.d and sdw1.a alleles have only been detected in the modern barley varieties and lines.ConclusionsThe results provided further proof that the gibberellin 20-oxidase gene (HvGA20ox2) is the functional gene of the barley sdw1 mutants. Different deletions resulted in different functional alleles for different breeding purposes. Truncated protein could maintain partial function. Partial or total loss of function of the HvGA20ox2 gene could be compensated by enhanced expression of its homolog HvGA20ox1 and HvGA20ox3. Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0964-4) contains supplementary material, which is available to authorized users.