How to awaken a sleeping giant: antagonistic expression of Flowering locus T homologs and elements of the age-related pathway are associated with the flowering transition in Agave tequilana.

KEY MESSAGE: Antagonistic expression of Flowering locus T proteins and the ageing pathway via miRNAs and sugar metabolism regulate the initiation of flowering in A. tequilana. Flowering in commercial plantations of Agave tequilana signals that plants are ready to harvest for tequila production. However, time of flowering is often unpredictable and a detailed understanding of the process would be beneficial in the field, for breeding and for the development of future research. This report describes the functional analysis of A. tequilana FLOWERING LOCUS T (FT) genes by heterologous expression in A. thaliana and in situ hybridization in agave plants. The gene structures of the Agave tequilana FT family are also described and putative regulatory promoter elements were identified. Most Agave species have monocarpic, perennial life cycles that can last over 25 years during which plants do not respond to the normal environmental signals which induce flowering, suggesting that the ageing pathway as described in Arabidopsis may play an important role in determining flowering time in these species. Elements of this pathway were analyzed and in silico data is presented that supports the regulation of SQUAMOSA PROMOTER BINDING LIKE proteins (SPL), APETALA2 (AP2) proteins and members of Plant Glycoside Hydrolase Family 32 (PGHF32) by interactions with miRNAs 156, 172 and 164 during the initiation of flowering in A. tequilana.

Advances in the Micropropagation and Genetic Transformation of Agave Species.

The Agave genus is composed of approximately 210 species distributed from south United States to Colombia and Venezuela. Numerous Agave species have been used for the preparation of alcoholic beverages and have attracted interest in the pharmaceutical and food industry. Despite their economic importance, there are few initiatives for the improvement and selection of characteristics of interest. This is mainly due to its morphology, long lifecycles, and monocarpic nature. Micropropagation is a feasible alternative to the improvement of Agave species. It has been used for multiple purposes, including massive propagation, induction of somaclonal variation to enhance agronomic characteristics of interest, maintenance of specific genotypes, and genetic transformation using molecular techniques. In this report, we summarize the most outstanding findings regarding the micropropagation of Agave species mediated by multiple regeneration responses. We also describe the media and growth regulators for each of the previously described methods. In addition, we discuss how micropropagation has allowed the development of transformation protocols. Exploitation of this technology may be a feasible strategy to introduce genes and improve certain traits. Genetic transformation also offers an opportunity for studying molecular mechanisms. This represents advantages for optimizing production in the field and for implementing breeding programs.