Guo-Ming Xing

AP2/ERF Transcription Factors Involved in Response to Tomato Yellow Leaf Curly Virus in Tomato

SlAP2/ERF factors respond to the TYLCV infection. GCC‐box binding ability of SlERF factors was different in tomato cultivars. SlERFs interact with other proteins in tomato. The defense mechanism to TYLCV is a complicated network.

Elevated Carbon Dioxide Altered Morphological and Anatomical Characteristics, Ascorbic Acid Accumulation, and Related Gene Expression during Taproot Development in Carrots

The CO2 concentration in the atmosphere has increased significantly in recent decades and is projected to rise in the future. The effects of elevated CO2 concentrations on morphological and anatomical characteristics, and nutrient accumulation have been determined in several plant species. Carrot is an important vegetable and the effects of elevated CO2 on carrots remain unclear. To investigate the effects of elevated CO2 on the growth of carrots, two carrot cultivars (‘Kurodagosun’ and ‘Deep purple’) were treated with ambient CO2 (a[CO2], 400 μmol⋅mol-1) and elevated CO2 (e[CO2], 3000 μmol⋅mol-1) concentrations. Under e[CO2] conditions, taproot and shoot fresh weights and the root/shoot ratio of carrot significantly decreased as compared with the control group. Elevated CO2 resulted in obvious changes in anatomy and ascorbic acid accumulation in carrot roots. Moreover, the transcript profiles of 12 genes related to AsA biosynthesis and recycling were altered in response to e[CO2]. The ‘Kurodagosun’ and ‘Deep purple’ carrots differed in sensitivity to e[CO2]. The inhibited carrot taproot and shoot growth treated with e[CO2] could partly lead to changes in xylem development. This study provided novel insights into the effects of e[CO2] on the growth and development of carrots.

Agrobacterium-mediated transformation of tomato (Lycopersicon esculentum L. cv. Hezuo 908) with improved efficiency

We developed an efficient and rapid Agrobacterium-mediated tomato transformation protocol by using cotyledon and hypocotyl as explants. The transgenic nature of the regenerants was confirmed through β-glucuronidase activity staining, polymerase chain reaction (PCR), quantitative real-time PCR (qPCR) analysis and northern blot analysis. In the used protocol, the optimized experimental conditions of the tomato genetic transformation were Agrobacterium liquid concentration, equivalent to optical density (OD600) of 1.0, 20 min (cotyledon) or 30 min (hypocotyl) infection time and 2 d of co-culturing period. The optimized medium for shoot induction was Murashige & Skoog (MS) medium + 0.5 mg/L indole-3-acetic acid (IAA) + 0.5 mg/L 6-benzylaminopurine (BAP) for cotyledon and MS + 0.5 mg/L IAA + 2.0 mg/L BAP for hypocotyl. The root induction rate was the highest on the MS medium, supplemented with 0.1 mg/L IAA. The transformation frequency reached 40% per explant. The received results are a base for a larger scale development of transformation procedure.

Regulation of abscisic acid biosynthesis and signal transduction during carrot growth and development

ABSTRACT Abscisic acid (ABA) is a common plant hormone that participates in growth and development processes and responds to abiotic stress. Carrot is a globally highly appreciated vegetable crop that shows obvious changes in tissues during growth. However, limited studies have investigated ABA biosynthesis and signalling in carrot. In this study, the ABA levels and expression levels of ABA-related genes in the roots, leaf blades, and petioles of carrot at five successive growth stages were measured. The endogenous ABA levels changed with the carrot tissue and growth stage. ABA content was highest in the leaf blades at each growth stage, and higher in the petioles than in the roots, except at Stage 2. The expression levels of most ABA-related genes were also highest in the leaf blades. The genes whose expression trends could reflect the ABA content may change with tissue in carrot. The results also indicated that the genes related to ABA biosynthesis and signal transduction may be influenced not only by ABA but also by other regulatory mechanisms such as carotenogenesis in carrot.

DcC4H and DcPER Are Important in Dynamic Changes of Lignin Content in Carrot Roots under Elevated Carbon Dioxide Stress

In our study, isobaric tags for relative and absolute quantification (iTRAQ) was conducted to determine the significantly changed proteins in the fleshy roots of carrots under different carbon dioxide (CO2) treatments. A total of 1523 proteins were identified, of which 257 were differentially expressed proteins (DEPs). On the basis of annotation analysis, the DEPs were identified to be involved in energy metabolism, carbohydrate metabolism, and some other metabolic processes. DcC4H and DcPER, two lignin-related proteins, were identified from the DEPs. Under elevated CO2 stress, both carrot lignin content and the expression profiles of lignin biosynthesis genes changed significantly. The protein-protein interactions among lignin-related enzymes proved the importance of DcC4H and DcPER. The results of our study provided potential new insights into the molecular mechanism of lignin content changes in carrot roots under elevated CO2 stress.

Genetic Regulation of GA Metabolism during Vernalization, Floral Bud Initiation and Development in Pak Choi (Brassica rapa ssp. chinensis Makino)

Pak choi (Brassica rapa ssp. chinensis Makino) is a representative seed vernalization vegetable and premature bolting in spring can cause significant economic loss. Thus, it is critical to elucidate the mechanism of molecular regulation of vernalization and floral bud initiation to prevent premature bolting. Gibberellin (GA) is the key plant hormone involved in regulating plant development. To gain a better understanding of GA metabolism in pak choi, the content of GA in pak choi was measured at different stages of plant development using enzyme-linked immunosorbent assay. The results showed that the GA content increased significantly after low-temperature treatment (4°C) and then decreased rapidly with vegetative growth. During floral bud initiation, the GA content increased rapidly until it peaked upon floral bud differentiation. To elucidate these changes in GA content, the expression of homologous genes encoding enzymes directly involved in GA metabolism were analyzed. The results showed that the changes in the expression of four genes involved in GA synthesis (Bra035120 encoding ent-kaurene synthase, Bra009868 encoding ent-kaurene oxidase, Bra015394 encoding ent-kaurenoic acid oxidase, and Bra013890 encoding GA20-oxidase) were correlated with the changes in GA content. In addition, by comparing the expression of genes involved in GA metabolism at different growth stages, seven differentially expressed genes (Bra005596, Bra009285, Bra022565, Bra008362, Bra033324, Bra010802, and Bra030500) were identified. The differential expression of these genes were directly correlated with changes in GA content, suggesting that these genes were directly related to vernalization, floral bud initiation and development. These results contribute to the understanding of the molecular mechanism of changes in GA content during different developmental phases in pak choi.

Digital gene expression analysis during floral transition in pak choi (Brassica rapa subsp. chinensis)

Digital gene expression profiling technology was used to examine the changes in gene expression during floral transition in pak choi. A total of 1486 differentially expressed genes (DEGs) during floral transition were identified, of which 505 were upregulated and 981 were downregulated. Gene ontology enrichment analysis showed that the proteins encoded by DEGs were mainly located in eight cell regions including the apoplast, plant-type cell wall, chloroplast, etc. They had eight kinds of molecular functions such as transcription factor and oxidoreductase, and involved in 72 biological processes containing jasmonic acid and salicylic acid metabolism, glucose metabolism, the MAPK cascade, etc. Further pathway enrichment analysis showed that four metabolic pathways were significantly enriched by DEGs. DEGs that exhibited at least a 10-fold difference were analyzed in detail. Results showed that flavonoid metabolism and phenylpropanoid biosynthesis (or pathways) were significantly enriched and the corresponding gene number was the highest. Moreover, 15 genes among the highly expressed genes were involved in reproductive development, of which five homologues in Arabidopsis thaliana were directly related to floral transition, which were predicted to have a similar function in pak choi.

Cloning and expression analysis of SPL8 homolog from pak choi (Brassica rapa subsp. chinensis)

ABSTRACT SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) transcription factor genes are functionally diverse; they control a number of fundamental aspects of plant growth and development, including vegetative phase change, flowering time, branching and leaf initiation rate. In our previous study, expression profiling showed that Bra033221, a transcript-derived fragment of an AtSPL8 ortholog, was up-regulated at flower bud differentiation stage 5. This result suggested that Bra033221 has a function similar to that of AtSPL8. In the present study, BrcSPL8, an AtSPL8 homolog, was cloned from pak choi (Brassica rapa subsp. chinensis) based on Bra033221 using reverse transcription-polymerase chain reaction (RT-PCR). The full-length cDNA was 1117 bp and contained a complete open reading frame (ORF) of 987 bp; this ORF encoded a predicted protein with 328 amino acid residues, a calculated molecular mass of 36.55 kDa and an isoelectric point of 8.85. BrcSPL8 was expressed in all analysed apices. Its expression levels before flower differentiation stage 1 were low and almost invariable, and the highest expression was detected in the apex at flower differentiation stage 5, suggesting that BrcSPL8 has a role during flower development in pak choi.

Cloning and Bioinformatic Analysis of a Novel Thiolase II Gene (BPLTHI2) from Betula Platyphylla

ABSTRACT A full-length cDNA sequence encoding a thiolase II of Betula platyphylla was identified from a constructed cDNA-AFLP library and obtained by the rapid amplification of cDNA ends (RACE) method. The cDNA gene, designated as BplTHI2, is 1 203 bp in length and encodes an enzyme of 400 amino acid residues with a calculated MW of 40.9 kDa. The BplTHI2 displays high similarity to the thiolase II of Camellia oleifera (90 % sequence identity) and Populus trichocarpa (89 %). It was predicted to possess two main domains, an N-terminal domain (10–268) and a C-terminal domain (278–398), which contain three predicted active sites (Cys96, His356 and Cys386). Its three-dimensional structure was predicted based on the crystal structure of human mitochondria thiolase (2ib8B). Expression analysis of the BplTHI2 gene showed that it was highly expressed in female inflorescences and not expressed in male ones. We suggest that BplTHI2 is a female inflorescence-specific gene and may be responsible for the development of female inflorescence.

Molecular Analysis of Differentially Expressed Genes in Birch (Betula Platyphylla) Inflorescence

ABSTRACT Birch (Betula platyphylla) has been widely applied in furniture, paper-making, and architecture for its special properties. One of the major problems is it has a long juvenile phase which limits the possibilities for production and application in these industries. To date, the molecular mechanism and biochemical pathways of the long juvenile phase are poorly understood. In this study, cDNA-Amplified Fragment Length Polymorphism (cDNA-AFLP) technique was used to analyze genes specifically expressed in the male or female inflorescence of birch. More than 7,000 TDFs (Transcript Derived Fragments) were screened by using 100 primer combinations. Of them, 168 male and 103 female inflorescence specific TDFs were isolated, subcloned and sequenced. About 54% of these TDFs were found to be similar with known genes in NCBI databases. Through GO annotation and KEGG pathway analysis, the results indicated that the male inflorescence of B. platyphylla possesses nearly two-fold more transcripts than the female inflorescence in energy production and conversion.