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PubMed2026

Genome-wide identification of WOX transcription factors and functional characterization of WOX4 and WOX13 involved in cold stress response in Malus baccata.

INTRODUCTION: Cold stress is a major abiotic threat to apple production. Malus baccata has exceptional cold hardiness and is widely used as a superior cold-resistant rootstock. The WUSCHEL-related homeobox (WOX) transcription factor family regulates plant growth, development and stress adaptation, whereas the functions of WOX genes in cold tolerance of M. baccata remain elusive. METHODS: In the present work, 19 MbWOX family members were identified and characterized at the genome-wide level. Evolutionary analysis, cis-element prediction, transcriptome profiling and real-time quantitative PCR (RT-qPCR) were performed to screen core cold-responsive genes. Overexpression vectors were constructed and transformed into Arabidopsis seedlings for functional verification. RESULTS: Evolutionary analysis revealed that segmental duplication drove the expansion of the MbWOX family, and these genes contained a variety of stress-responsive cis-elements. Combined transcriptome and RT-qPCR analyses confirmed that MbWOX4 and MbWOX13 were core cold-responsive genes with distinct expression patterns. The two genes participated in cold signal transduction by interacting with different transcription factor networks. Functional tests revealed that MbWOX4 and MbWOX13 isoforms differentially modulated seedling cold tolerance under low-temperature stress.

Malus baccata↗

PubMed2004

Molecular markers linked to the apple scab resistance gene Vbj derived from Malus baccata jackii.

Breeding for scab-resistant apple cultivars by pyramiding several resistance genes in the same genetic background is a promising way to control apple scab caused by the fungus Venturia inaequalis. To achieve this goal, DNA markers linked to the genes of interest are required in order to select seedlings with the desired resistance allele combinations. For several apple scab resistance genes, molecular markers are already available; but until now, none existed for the apple scab resistance gene Vbj originating from the crab apple Malus baccata jackii. Using bulk segregant analysis, three RAPD markers linked to Vbj were first identified. These markers were transformed into more reliable sequence-characterised amplified region (SCAR) markers that proved to be co-dominant. In addition, three SSR markers and one SCAR were identified by comparing homologous linkage groups of existing genetic maps. Discarding plants showing genotype-phenotype incongruence (GPI plants) plants, a linkage map was calculated. Vbj mapped between the markers CH05e03 (SSR) and T6-SCAR, at 0.6 cM from CH05e03 and at 3.9 cM from T6-SCAR. Without the removal of the GPI plants, Vbj was placed 15 cM away from the closest markers. Problems and pitfalls due to GPI plants and the consequences for mapping the resistance gene accurately are discussed. Finally, the usefulness of co-dominant markers for pedigree analysis is also demonstrated.

Ascomycota↗

PubMed2005

[Growth responses of four northern broadleaved tree species to soil Cd stress].

In this paper, the gradient (0, 10, 50, 100, 200 mg x kg(-1)) of soil Cd concentrations was established by mixing CdCl2 with soil and sand, and the growth responses of four northern broadleaved tree species Acer ginnala Pyrus ussuriensis, Acer mono and Malus baccata to soil Cd contamination were studied by growing their seedlings in pots in greenhouse. The results revealed that the seedling growth of all test species was enhanced under lower soil Cd concentrations (< or = 50 mg x kg(-1)), and Acer ginnala had the strongest response under 10 mg x kg(-1) treatment, with 135.8% and 146.0% increment of collar and height growth, respectively, in comparing with the control. But, the growth of aboveground part decreased with increasing soil Cd, and the collar and height growth of A. ginnala under the highest Cd concentration was only 24.1% and 28.0% of the control, respectively. Under lower Cd concentrations, an increase of foliage and new shoot growth was found in A. ginnala and P. ussuriensis, the biomass of new shoots increased but that of foliage decreased in M. baccata, and both foliage and new shoot decreased in A. mono. Under the highest Cd concentration, A. ginnala had the greatest decrease of foliage and new shoot biomass, being 4.6% and 7.3% of the control, respectively, while P. ussuriensis and M. baccata had a relatively less decrease. The biomass increase of new roots declined with increasing Cd concentration for all tree species except P. ussuriensis, and the least increase was A. ginnala, only 2.3% of the control. The new root biomass of P. ussuriensis was 125.5% and 117.1% of the control at 10 mg and 20 mg x kg(-1), respectively. The total biomass increment of A. ginnala and P. ussuriensis seedlings was greater than that of the control under lower Cd concentrations, while an obvious decrease was found for all tree species under higher Cd concentrations. Under the highest Cd concentration, the total biomass of A. ginnala, M. baccata, A. mono and P. ussuriensis was 13.7%, 27.2%, 36.4 and 40.1% of the control, respectively. Subordinate function analysis suggested that the tolerance of test tree species to soil Cd contamination was in order of M. baccata > A. ginnala > P. ussuriensis > A. mono. Analysis of Cd concentration in plant tissues demonstrated that P. ussuriensis had the highest Cd enrichment coefficient for its root, shoot and foliage, and M. baccata also had a higher Cd enrichment in its root and shoot.

Acer↗

PubMed1990

Response of five temperate deciduous tree species to water stress.

Gas exchange, tissue water relations, and leaf/root dry weight ratios were compared among young, container-grown plants of five temperate-zone, deciduous tree species (Acer negundo L., Betula papyrifera Marsh, Malus baccata Borkh, Robinia pseudoacacia L., and Ulmus parvifolia Jacq.) under well-watered and water-stressed conditions. There was a small decrease (mean reduction of 0.22 MPa across species) in the water potential at which turgor was lost (Psi(tlp)) in response to water stress. The Psi(tlp) for water-stressed plants was -1.18, -1.34, -1.61, -1.70, and -2.12 MPa for B. papyrifera, A. negundo, U. parvifolia, R. pseudoacacia, and M. baccata, respectively. Variation in Psi(tlp) resulted primarily from differences in tissue osmotic potential and not tissue elasticity. Rates of net photosynthesis declined in response to water stress. However, despite differences in Psi(tlp), there were no differences in net photosynthesis among water-stressed plants under the conditions of water stress imposed. In A. negundo and M. baccata, water use efficiency (net photosynthesis/transpiration) increased significantly in response to water stress. Comparisons among water-stressed plants showed that water use efficiency for M. baccata was greater than for B. papyrifera or U. parvifolia. There were no significant differences in water use efficiency among B. papyrifera, U. parvifolia, A. negundo, and R. pseudoacacia. Under water-stressed conditions, leaf/root dry weight ratios (an index of transpiration to absorptive capacity) ranged from 0.77 in R. pseudoacacia to 1.05 in B. papyrifera.

Journal Article↗

PubMed2004

[Impact of automobile exhaust on membrane lipid peroxidation and protective enzyme activities in seedlings foliage of four northern broadleaved tree species].

By means of fumigating one-year-old seedlings in open top chambers, this paper studied the impact of automobile exhaust on the pH value, relative conductivity, malondialdehyde (MDA) and chlorophyll contents, superoxide dismutase (SOD) and peroxidase (POD) activities, and ascorbic acid (ASA) content in the seedlings foliage of four tree species, Acer mono, Malus baccata, Prunus ussuriensis, and Acer ginnala. During the fumigation, the seedlings were exposed to the same exhaust gas concentration (25 microg x m(-3), indicated by the NO2 concentration in exhaust) for different durations (1, 3, 5, 7 d), and to different concentrations (40, 60, 80, 100 microg NO2 x m(-3)) for same duration (2 h). The results showed that the pH value and the chlorophyll and ascorbic acid (ASA) contents decreased, whereas the relative conductivity, malondialdehyde (MDA) content, and superoxide dismutase (SOD) and peroxidase (POD) activities increased with increasing fumigation duration and exhaust concentration. Obvious interspecies variations in term of physiological features were found. After treated 7 days with 25 microg NO2 x m(-3) and treated 2 h with 100 microg NO2 x m(-3), only a 1.5% and 2.7% decrease of cell juice pH was found in A. ginnala, respectively, compared to the control. The corresponding data for P. ussuriensis was 9.42% and 13.89%, followed by M. baccata. The chlorophyll content of A. mono, A. ginnala, M. baccata and P. ussuriensis was 83.0%, 71.3%, 68.7% and 54.9%, respectively of the control after 7 days treated with 25 microg NO2 x m(-3), and the corresponding data under 100 microg NO2 x m(-3) treatment was 60.2%, 73.1%, 43.4% and 51.2%, respectively. The decrease of ASA content and Acer ginnala was less in A. mono than in M. baccata and P. ussuriensis. The relative conductivity and MDA content of A. mono increased respectively by 68.1% and 52.5% in compared with control, while those of A. ginnala had the least increment. As for the 100 microg NO2 x m(-3) treatment, the maximum increases of relative conductivity (99.8%) and MDA content (52.5%) were found in M. baccata, while the least were found in A. mono and A. ginnala. The SOD and POD activities generally increased under the highest concentration of exhaust, with the exception of M. baccata. To summarize, almost all the test physiological features of A. ginnala were least affected, suggesting its great tolerance to exhaust stress, but in contrary, the greatest variation of the physiological features and the dramatic decline of SOD and POD activities of M. baccata at the highest exhaust concentration indicated that this tree species had the least tolerance to exhaust stress.

Chlorophyll↗

PubMed2003

Comparative analysis of superfamilies of NBS-encoding disease resistance gene analogs in cultivated and wild apple species.

Eleven distinct families of resistance gene analogs (RGAs) with the characteristic nucleotide-binding sequence (NBS) were identified in two wild apple species, Malus prunifolia and M. baccata, and two cultivated apple cultivars, M. domestica cv. Fuji and M. domestica cv. Hong-ok, using PCR approaches with degenerate primers based on two conserved motifs of known NBS-LRR resistance genes. These RGA families were found to be represented in all the apple species tested, including wild and cultivated species. However, their sequences are very divergent from each other. Furthermore, the low level of recombination detected within their RGA families supports the idea that the evolution of NBS-encoding sequences in apple species involves the gradual accumulation of mutations. Despite the high diversity of the RGA families found in all apple species, the apparent lack of differentiation between wild and cultivated forms suggests that other factors, such as the capacity to tolerate pathogens, might play an important role in the survival of wild-type species.

Amino Acid Sequence↗

PubMed2006

Mapping of the apple scab-resistance gene Vb.

Apple scab, caused by the fungus Venturia inaequalis, is the major production constraint in temperate zones with humid springs. Normally, its control relies on frequent and regular fungicide applications. Because this control strategy has come under increasing criticism, major efforts are being directed toward the breeding of scab-resistant apple cultivars. Modern apple breeding programs include the use of molecular markers, making it possible to combine several different scab-resistance genes in 1 apple cultivar (pyramiding) and to speed up the breeding process. The apple scab-resistance gene Vb is derived from the Siberian crab apple 'Hansen's baccata #2', and is 1 of the 6 "historical" major apple scab-resistance genes (Vf, Va, Vr, Vbj, Vm, and Vb). Molecular markers have been published for all these genes, except Vr. In testcross experiments conducted in the 1960s, it was reported that Vb segregated independently from 3 other major resistance genes, including Vf. Recently, however, Vb and Vf have both been mapped on linkage group 1, a result that contrasts with the findings from former testcross experiments. In this study, simple sequence repeat (SSR) markers were used to identify the precise position of Vb in a cross of 'Golden Delicious' (vbvb) and 'Hansen's baccata #2' (Vbvb). A genome scanning approach, a fast method already used to map apple scab-resistance genes Vr2 and Vm, was used, and the Vb locus was identified on linkage group 12, between the SSR markers Hi02d05 and Hi07f01. This finding confirms the independent segregation of Vb from Vf. With the identification of SSR markers linked to Vb, another major apple scab-resistance gene has become available; breeders can use it to develop durable resistant cultivars with several different resistance genes.

Ascomycota↗