UDP-glucose pyrophosphorylase (UGPase) is an important enzyme in the metabolism of UDP-glucose, a precursor for the synthesis of carbohydrate cell wall components, such as cellulose and callose. The Arabidopsis thaliana genome contains two putative genes encoding UGPase, AtUGP1 and AtUGP2. These genes are expressed in all organs. In order to determine the role of UGPase in vegetative and reproductive organs, we employed a reverse genetic approach using the T-DNA insertion mutants, atugp1 and atugp2. Despite a significant decrease in UGPase activity in both the atugp1 and atugp2 single mutants, no decrease in normal growth and reproduction was observed. In contrast, the atugp1/atugp2 double mutant displayed drastic growth defects and male sterility. At the reproductive phase, in the anthers of atugp1/atugp2, pollen mother cells developed normally, but callose deposition around microspores was absent. Genes coding for enzymes at the subsequent steps in the cellulose and callose synthesis pathway were also down-regulated in the double mutant. Taken together, these results demonstrate that the AtUGP1 and AtUGP2 genes are functionally redundant and UGPase activity is essential for both vegetative and reproductive phases in Arabidopsis. Importantly, male fertility was not restored in the double knockout mutant by an application of external sucrose, whereas vegetative growth was comparable in size with that of the wild type. In contrast, an application of external UDP-glucose recovered male fertility in the double mutant, suggesting that control of UGPase in carbohydrate metabolism is different in the vegetative phase as compared with the reproductive phase in A. thaliana.
Clubroot is a devastating disease caused by Plasmodiophora brassicae and results in severe losses of yield and quality in Brassica crops. Many clubroot resistance genes and markers are available in Brassica rapa but less is known in Brassica oleracea. Here, we applied the genotyping-by-sequencing (GBS) technique to construct a high-resolution genetic map and identify clubroot resistance (CR) genes. A total of 43,821 SNPs were identified using GBS data for two parental lines, one resistant and one susceptible lines to clubroot, and 18,187 of them showed >5× coverage in the GBS data. Among those, 4,103 were credibly genotyped for all 78 F2 individual plants. These markers were clustered into nine linkage groups spanning 879.9 cM with an average interval of 1.15 cM. Quantitative trait loci (QTLs) survey based on three rounds of clubroot resistance tests using F2 : 3 progenies revealed two and single major QTLs for Race 2 and Race 9 of P. brassicae, respectively. The QTLs show similar locations to the previously reported CR loci for Race 4 in B. oleracea but are in different positions from any of the CR loci found in B. rapa. We utilized two reference genome sequences in this study. The high-resolution genetic map developed herein allowed us to reposition 37 and 2 misanchored scaffolds in the 02–12 and TO1000DH genome sequences, respectively. Our data also support additional positioning of two unanchored 3.3 Mb scaffolds into the 02–12 genome sequence.
BackgroundZinc finger homeodomain proteins (ZHD) constitute a plant-specific transcription factor family with a conserved DNA binding homeodomain and a zinc finger motif. Members of the ZHD protein family play important roles in plant growth, development, and stress responses. Genome-wide characterization of ZHD genes has been carried out in several model plants, including Arabidopsis thaliana and Oryza sativa, but not yet in tomato (Solanum lycopersicum).ResultsIn this study, we performed the first comprehensive genome-wide characterization and expression profiling of the ZHD gene family in tomato (Solanum lycopersicum). We identified 22 SlZHD genes and classified them into six subfamilies based on phylogeny. The SlZHD genes were generally conserved in each subfamily, with minor variations in gene structure and motif distribution. The 22 SlZHD genes were distributed on six of the 12 tomato chromosomes, with segmental duplication detected in four genes. Analysis of Ka/Ks ratios revealed that the duplicated genes are under negative or purifying selection. Comprehensive expression analysis revealed that the SlZHD genes are widely expressed in various tissues, with most genes preferentially expressed in flower buds compared to other tissues. Moreover, many of the genes are responsive to abiotic stress and phytohormone treatment.ConclusionSystematic analysis revealed structural diversity among tomato ZHD proteins, which indicates the possibility for diverse roles of SlZHD genes in different developmental stages as well as in response to abiotic stresses. Our expression analysis of SlZHD genes in various tissues/organs and under various abiotic stress and phytohormone treatments sheds light on their functional divergence. Our findings represent a valuable resource for further analysis to explore the biological functions of tomato ZHD genes.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4082-y) contains supplementary material, which is available to authorized users.
Growth regulating factors (GRFs) are plant-specific transcription factors that are involved in diverse biological and physiological processes, such as growth, development and stress and hormone responses. However, the roles of GRFs in vegetative and reproductive growth, development and stress responses in tomato (Solanum lycopersicum) have not been extensively explored. In this study, we characterized the 13 SlGRF genes. In silico analysis of protein motif organization, intron–exon distribution, and phylogenetic classification confirmed the presence of GRF proteins in tomato. The tissue-specific expression analysis revealed that most of the SlGRF genes were preferentially expressed in young and growing tissues such as flower buds and meristems, suggesting that SlGRFs are important during growth and development of these tissues. Some of the SlGRF genes were preferentially expressed in fruits at distinct developmental stages suggesting their involvement in fruit development and the ripening process. The strong and differential expression of different SlGRFs under NaCl, drought, heat, cold, abscisic acid (ABA), and jasmonic acid (JA) treatment, predict possible functions for these genes in stress responses in addition to their growth regulatory functions. Further, differential expression of SlGRF genes upon gibberellic acid (GA3) treatment indicates their probable function in flower development and stress responses through a gibberellic acid (GA)-mediated pathway. The results of this study provide a basis for further functional analysis and characterization of this important gene family in tomato.
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