Heterotrimeric G proteins composed of α, β, and γ subunits are central signal transducers mediating the cellular response to multiple stimuli in most eukaryotes. Gγ subunits provide proper cellular localization and functional specificity to the heterotrimer complex. Plant Gγ subunits, divided into three structurally distinct types, are more diverse than their animal counterparts. Type B Gγ subunits, lacking a carboxyl-terminal isoprenylation motif, are found only in flowering plants. We present the functional characterization of type B Gγ subunit (SlGGB1) in tomato (Solanum lycopersicum). We show that SlGGB1 is the most abundant Gγ subunit in tomato and strongly interacts with the Gβ subunit. Importantly, the green fluorescent protein-SlGGB1 fusion protein as well as the carboxyl-terminal yellow fluorescent protein-SlGGB1/amino-terminal yellow fluorescent protein-Gβ heterodimer were localized in the plasma membrane, nucleus, and cytoplasm. RNA interference-mediated silencing of SlGGB1 resulted in smaller seeds, higher number of lateral roots, and pointy fruits. The silenced lines were hypersensitive to exogenous auxin, while levels of endogenous auxins were lower or similar to those of the wild type. SlGGB1-silenced plants also showed strong hyposensitivity to abscisic acid (ABA) during seed germination but not in other related assays. Transcriptome analysis of the transgenic seeds revealed abnormal expression of genes involved in ABA sensing, signaling, and response. We conclude that the type B Gγ subunit SlGGB1 mediates auxin and ABA signaling in tomato.

Annonaceae is an ancient family of plants including approximately 50 genera growing worldwide in a quite restricted area with specific agroclimatic requirements. Only few species of this family has been cultivated and exploited commercially and most of them belonging to the genus Annona such as A. muricata, A. squamosa, the hybrid A. cherimola x A. squamosa and specially Annona cherimola: the cherimoya, commercially cultivated in Spain, Chile, California, Florida, México, Australia, Ecuador, Peru, Brazil, New Zealand and several countries in South and Central America. The cherimoya shows a high degree of heterozygosis, and to obtain homogeneous and productive orchards it is necessary to avoid the propagation by seeds of this species. Additionally, the traditional methods of vegetative propagation were inefficient and inadequate, due to the low morphogenetic potential of this species, and the low rooting rate. The in vitro tissue culture methods of micropropagation can be applied successfully to cherimoya and other Annona sp to overcome these problems. Most of the protocols of micropropagation and regeneration were developed using the cultivar Fino de Jete, which is the major cultivar in Spain. First it is developed the method to micropropagate the juvenile material of cherimoya (ENCINA et al., 1994), and later it was optimized a protocol to micropropagate adult cherimoya genotypes selected by outstanding agronomical traits (PADILLA and ENCINA, 2004) and further it was improved the process through micrografting (PADILLA and ENCINA, 2011).At the present time we are involved in inducing and obtaining new elite genotypes, as part of a breeding program for the cherimoya and other Annonas, using and optimizing different methodologies in vitro: a) Adventitious organogenesis and regeneration from cellular cultures (ENCINA, 2004), b) Ploidy manipulation of the cherimoya, to obtain haploid, tetraploid and triploid plants (seedless), c) Genetic transformation, for the genes introduction to control the postharvest processes and the genes introduction to provide resistance to pathogen and insects and d) Micropropagation and regeneration of other wild Annona or related Annonaceae species such as: Annona senegalensis, A. scleroderma, A. montana, A. reticulata, A. glabra, A. diversifolia and Rollinia sp.

In vitro plant tissue culture and biotechnology used to assist and support the development of plant breeding when classical methods of propagation must be accelerated or it was necessary to overcome barriers inaccessible by classical approaches. In asparagus, to improve multiple breeding tasks, a high number of in vitro methods have been used, such as plant regeneration methods through organogenesis, embryogenesis, manipulation of ploidy, protoplast isolation, genetic manipulation (protoplast fusion, genetic transformation), embryo rescue and germplasm preservation (in vitro, in vitro slow growth, cryopreservation). Plant tissue culture methods can overcome multiple problems in asparagus breeding such as, barriers of self and cross-incompatibility between asparagus species through embryo rescue of interspecific hybrids and protoplast fusion or genetic transformation, introgression of new genes, clonal propagation of elite genotypes of asparagus, mass screening, and the generation of haploid and polyploid genotypes, among others, becoming the tool of choice for asparagus breeding programs. Some of these in vitro methods are still under development.

In this article, we present proliferation data from 10 years of the continuous in vitro incubation of cv. Solo papaya shoots and propose a reliable method for the long-term micropropagation of papaya, using microshoots developed from the axillary buds of papaya shoots as primary explants. Three different media were assayed. The proliferation medium (PPRM) allowed us to maintain papaya shoots under continuous proliferation for 20 years, maintaining consistent behavior. Most of the shoots developed in the PPRM rooted during the incubation and then acclimated easily, maintaining the ploidy and morphological characteristics of the parental plants, and flowering and setting fruits normally. The PPRM medium consisted of MS medium supplemented with naphthalene acetic acid (NAA) (0.1 mg L⁻¹), benzyladenine (BA) (0.5 mg L⁻¹), gibberellic acid (GA₃) (0.5 mg L⁻¹), and adenine hemisulphate (40 mg L⁻¹). The average multiplication rate was higher than 20 shoots per explant during the long-term assay. The elongation medium (PELM) was designed to recover shoots with poor growth and allowed the development of high-quality shoots ready for rooting. It consisted of an MS basal medium supplemented with NAA (0.1 mg L⁻¹), kinetin (KIN) (0.5 mg L⁻¹), and GA₃ (1 mg L⁻¹). The rooting medium (PROM) was designed to induce high-quality roots from nonrooted shoots and consisted of a half-strength MS medium and indole-3-butiryc acid (IBA) (1 mg L⁻¹). On PROM, agar can be exchanged for expanded vermiculite. Acclimation took place inside an acclimatization tunnel under progressive hydric stress. After 4 weeks, the plant recovery rate was 90% for plants maintained under continuous proliferation for ten years. The main objective of this work was to provide a micropropagation method which would maintain healthy elite genotypes of papaya for long periods of time and produce a high number of good quality plants.

A micropropagation protocol for Pouteria lucuma R. and Pav. var. La Molina, was developed. Shoots from zygotic embryos with a portion of endosperm were established in vitro on Murashige and Skoog (MS) medium with 0.47 μM kinetin (Kin) and 0.54 μM naphthaleneacetic acid (NAA). Multiplication of shoots was accomplished using subapical, shoots. The best axillary-shoot production was observed on MS basal, medium with 2.2μM, benzyladenine (BA), 0.5 μM NAA, 1.4. μM gibberellic acid (GA₃), and 40 mgl⁻¹ adenine sulfate, with the development of up to three axillary shoots per subapical shoot. One hundred percent rooting was obtained from shoots grown, for 4wk on MS medium with 246 μM indole-3-butyric acid under light conditions. Eighty percent of the microplantlets survived after acclimatization when transplanted to a substrate previously enriched with beneficial soil bacteria. This study describes, for the first time, arbuscular mycorrhizal (AM) colonization of this species. Inoculation with AM fungi improved growth and development of lucumo plants and induced changes to the root morphology.