Anther culture and chromosome reduction in wheat × Thinopyrum wide crosses

Callus cultures of Ambrosia tenuifolia were established from sub-apical leaves. The explants were grown on basal media MS (Murashige and Skoog) supplemented with 10 μM kinetin, 1 μM 2-4 dichlorophenoxyacetic, ascorbic acid and cysteine and cultivated either in light or darkness. To determine the effect of each individual salt component on the growing rate of the callus and the psilostachyinolides and altamisine production in the culture, the concentrations of each nutrient was tested at different levels, ranging from 50% above to 50% below the standard medium. Interestingly, increased concentration of boron in the medium, resulted in a four fold increase in the production of sesquiterpene lactones by the callus. However, positive production of psilostachynolides and altamisine was only detected when the basal concentrations of the others components of the basal media were used. In addition, production of altamisine was highly sensitive to the variations of nutrients. No statiscally effect on terpenoide production by the callus was detected by varying light exposure. These results indicates that conditions for the optimal production of these terpenoids can be enhanced by modifying nutrients of the MS basal media. This revised version was published online in June 2006 with corrections to the Cover Date.     

Evaluation of genetic variability of sorghum (Sorghum bicolor L. Moench) in northwestern Morocco by ISSR and RAPD markers

The study of the genetic variability of the Moroccan landraces of sorghum constitutes a necessary step that can be exploited in the programs of improvement and valorisation of this marginalized species. The aim of this investigation is to evaluate the variability of sorghum populations and to establish their phylogenetic relations using RAPD and ISSR markers. Sampling was taken in 33 fields of northern regions where this species is most cultivated. Individual plants (398) were collected in 13, 11, 5, and 4 fields of Larache, Tangier, Chefchaouen, and Tetouan, respectively. Thirty-eight RAPD primers and four ISSR primers were used. The percentage of polymorphic fragments revealed with ISSR (98%) is higher than the one revealed with RAPD (85%). The level of the variability obtained through the two techniques is very high. Nevertheless, ISSR markers revealed more diversity than RAPD (0.995+/-0.006 against 0.946+/-0.031). The classification based on Jaccard's similarity index distinguished the totality of fields. Data analysis revealed a genetic structure that is closely related to the micro-geographical repartition of the different fields.     

Epigenetic regulation of surfactant protein A gene (SP-A) expression in fetal lung reveals a critical role for Suv39h methyltransferases during development and hypoxia

SP-A gene expression is developmentally regulated in fetal lung. Cyclic AMP (cAMP) induction of SP-A expression in human fetal lung type II cells is O(2) dependent and is mediated by increased binding of TTF-1/Nkx2.1 and NF-κB to a critical response element (TBE). This is associated with increased acetylation and decreased methylation of H3K9 at the TBE. Using chromatin immunoprecipitation analysis of fetal lung between 15.5 and 19.0 days of gestation, we observed that the developmental induction of SP-A was associated with increased recruitment of TTF-1, NF-κB, PCAF, and CBP, as well as enhanced acetylation and decreased methylation of histone H3K9 at the TBE. Importantly, expression and TBE binding of the H3K9 methyltransferases, Suv39h1 and Suv39h2, was inversely correlated with the developmental upregulation of SP-A. In human fetal lung epithelial cells, Suv39H1 and Suv39H2 mRNA levels declined with cAMP induction of SP-A. Moreover, hypoxia, which inhibits cAMP stimulation of SP-A, markedly increased Suv39h1 and Suv39h2 binding to the TBE. Finally, short hairpin RNA knockdown of Suv39H1 or Suv39H2 in fetal lung epithelial cells repressed H3K9 methylation and greatly enhanced SP-A expression. Collectively, our findings suggest that Suv39H1 and Suv39H2 are key hypoxia-induced methyltransferases; their decline in fetal lung during late gestation is critical for epigenetic changes resulting in the developmental induction of SP-A.     

Introgression and characterization of barley yellow dwarf virus resistance from Thinopyrum intermedium into wheat.

Wheatgrasses (species of Agropyron complex) have previously been reported to be resistant to barley yellow dwarf virus (BYDV). To introgress this resistance into wheat, Triticum aestivum x Thinopyrum (Agropyron) intermedium hybrids were advanced through a backcrossing program and reaction to BYDV, as determined by enzyme-linked immunosorbent assay (ELISA), is reported for the first time in backcross populations of wide hybrids between wheat and wheatgrasses. ELISA values revealed highly resistant to highly susceptible segregants in backcrosses. BYDV resistance was expressed in some backcross derivatives. Continued selection, based on cytology and ELISA in each generation, eliminated most of the unwanted wheatgrass chromosomes and produced self-fertile BYDV resistant wheat lines. The BYDV resistant lines with 2n = 42 had normal chromosome pairing similar to wheat, and their F1 hybrids with wheat had two univalents. DNA analyses showed that the source of alien chromatin in these BYDV resistant wheat lines is distinguishable from that in other Th. intermedium derived BYDV resistant wheat lines. Chromosome pairing and restriction fragment length polymorphism analyses indicated that the 42 chromosome resistant Purdue wheat lines are substitution lines in which chromosome 7D was replaced by a chromosome from Th. intermedium that was carrying gene(s) for BYDV resistance.     

Genotypic variation in anther culture and effect of ovary coculture in durum wheat

The response of anthers to in vitro culture and the effect of coculture of ovaries on anther culturability have been studied in responsive and recalcitrant cultivars of durum wheat (Triticum turgidum ssp. durum) from Morocco and ICARDA. A large genotypic-dependence of anther culture has been shown in 18 cultivars. Their response in term of callus and embryo induction varied from 0 to 13%. Coculture of ovaries with anthers enhanced the response of the most responsive genotype (cv. Sarif) and removed the recalcitrance in Cocorit and Isly cultivars. However, there was no effect of anther-ovary coculture on green plant regeneration. The implication of the genome and the media conditioning by the ovaries on anther response is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.