The mating-type switches in the yeast Saccharomyces cerevisiae occur by unidirectional transposition of replicas of unexpressed genetic information, residing at HML or HMR, into the mating-type locus (MAT). The source loci, HML and HMR, remain unchanged. Interestingly, when the HM cassettes are expressed, as in marl strains, the HML and HMR cassettes can also efficiently switch, apparently by obtaining genetic information from either of the other two cassettes (Klar et al., Cell 25:517-524, 1981). We have isolated a novel chromosome III rearrangement in heterothallic (marl ho) strains, which is also produced efficiently in marl HO cells, presumably the consequence of a recombination event between HML and HMR. The fusion results in the loss of sequences which are located distal to HML and to HMR and produces a ring derivative of chromosome III. Cells containing such a ring chromosome are viable as haploids; apparently, no essential loci are located distal to the HM loci. The fusion cassette behaves as a standard HM locus with respect to both regulation by the MARISIR control and its role in switching MAT.

BackgroundCoffee production relies on plantations with varieties from Coffea arabica and Coffea canephora species. The first, the most representative in terms of coffee consumption, is mostly propagated by seeds, which leads to management problems regarding the plantations maintenance, harvest and processing of grains. Therefore, an efficient clonal propagation process is required for this species cultivation, which is possible by reaching a scalable and cost-effective somatic embryogenesis protocol. A key process on somatic embryogenesis induction is the auxin homeostasis performed by Gretchen Hagen 3 (GH3) proteins through amino acid conjugation. In this study, the GH3 family members were identified on C. canephora genome, and by performing analysis related to gene and protein structure and transcriptomic profile on embryogenic tissues, we point a GH3 gene as a potential regulator of auxin homeostasis during early somatic embryogenesis in C. arabica plants.ResultsWe have searched within the published C. canephora genome and found 17 GH3 family members. We checked the conserved domains for GH3 proteins and clustered the members in three main groups according to phylogenetic relationships. We identified amino acids sets in four GH3 proteins that are related to acidic amino acid conjugation to auxin, and using a transcription factor (TF) network approach followed by RT-qPCR we analyzed their possible transcriptional regulators and expression profiles in cells with contrasting embryogenic potential in C. arabica. The CaGH3.15 expression pattern is the most correlated with embryogenic potential and with CaBBM, a C. arabica ortholog of a major somatic embryogenesis regulator.ConclusionTherefore, one out of the GH3 members may be influencing on coffee somatic embryogenesis by auxin conjugation with acidic amino acids, which leads to the phytohormone degradation. It is an indicative that this gene can serve as a molecular marker for coffee cells with embryogenic potential and needs to be further studied on how much determinant it is for this process. This work, together with future studies, can support the improvement of coffee clonal propagation through in vitro derived somatic embryos.

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ABSTRACT:Hancornia speciosa Gomes is a fruit species belonging to the Apocynaceae family and holds social, cultural and economic potential mostly due to its use in composition of many food industry products and the consumption its fruits in natura. Several aspects regarding their propagation need further studies, since the species is undergoing a continuous process of domestication. The objective was to obtain an in vitro protocol for indirect organogenesis and rooting with subsequent acclimatization of H. speciosa plants. To obtain indirect organogenesis, internodal segments were inoculated in WPM culture medium gelled with 7 g L -1 agar, added with 30 g L -1 sucrose, 0.4 g L -1 PVP, and supplied with different concentrations of 2,4-D (0.0; 2.46; 7.38; 12.30; and 17.22 µM), BAP (0.0; 4.92; 9.84; 14.76; and 19.68 µM), and TDZ (0.0; 4.92; 9.84; 14.76; and 19.68 µM). For the in vitro rooting, shootings with approximately 6.0 cm diameter length kept for 15 days in WPM medium with no plant growth regulator and, afterwards, subjected to treatments with different auxins (Control; 9.84 µM IBA; 9.84 µM NAA; and 9.84 µM IAA) as well as the combination among them, in order to verify their effects on percentage of rooting (%), number of roots, and average length of the largest root (cm). The formation of calluses was observed in all explants subjected to the concentrations of the regulators tested. The highest shooting regeneration occurred with 7.38 µM 2,4-D (73%). The highest percentage of shoot rooting (80%) and roots with the largest length (1.3 cm) were found in the culture medium with the combination of 4.92 µM NAA and 4.92 µM IBA. The in vitro regeneration of H. speciosa is feasible. The acclimatization of rooted shoots in Trospstrato® was accomplished with successful and 100% survival of plant material was observed during this stage.

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Anadenanthera colubrina is a species native to Brazil, from the Fabaceae family and has potential for use in the timber industry, in the reforestation of degraded areas, besides having medicinal properties. Its propagation is mainly by seeds, but basic subsidies regarding the requirements for optimal germination conditions are still lacking. Aiming to contribute to the expansion of its cultivation, rational use and conservation, the objective of this study was to investigate the morphology and anatomy of fruits and seeds, as well as the responses to factors as thermal regimes and substrates in seed germination. The 1000-seed weight and seeds per fruit were determined. To characterize the seed tissues, histochemical test with Sudan III and Lugol was used. The temperatures analyzed in the germination test were 15-25 °C; 25 °C; 20-30 °C and 30 °C. Different substrates for germination (paper rolls, paper sheet such as “germitest”, commercial substrate and sand) were also analyzed in the presence of light at 30 °C. The average number of seeds per fruit is 10 and the 1000-seed weight is 118 g. Germination is fast and high over a wide temperature range; however, the temperature of 25 °C contributes to a substantial increase in the percentage of abnormal seedlings and dead seeds, both in the absence and presence of light. A. colubrina seeds are indifferent to light and the highest vigor was verified at 30 °C. Sand and commercial substrates are efficient in initial seedling development.