Lorena Rodríguez-López

Together with their undeniable role in the ecology of arid and semiarid ecosystems, Agave species are emerging as a model to dissect the relationships between crassulacean acid metabolism and high efficiency of light and water use, and as an energy crop for bioethanol production. Transcriptome resources from economically valuable Agaves species, such as Agave tequilana and A. salmiana, as well as hybrids for fibers, are now available, and multiple gene expression landscape analyses have been reported. Key components in molecular mechanisms underlying drought tolerance could be uncovered by analyzing gene expression patterns of roots. This study describes an efficient protocol for high-quality total RNA isolation from phenolic compounds-rich Agave roots. Our methodology involves suitable root handling and collecting in the field and using saving-time commercial kits available. RNA isolated from roots free of lignified out-layers and clean cortex showed high values of quality and integrity according to electrophoresis and microfluidics-based platform. Synthesis of long full-length cDNAs and PCR amplification tested the suitability for downstream applications of extracted RNA. The protocol was applied successfully to A. tequilana roots but can be used for other Agave species that also develop lignified epidermis/exodermis in roots.

Spines are key plant modifications developed to deal against herbivores; however, its physical structure and chemical composition have been little explored in plant species. Here, we took advantage of high-throughput chromatography to characterize chemical composition of Agave fourcroydes Lem. spines, a species traditionally used for fiber extraction. Analyses of structural carbohydrate showed that spines have lower cellulose content than leaf fibers (52 and 72%, respectively) but contain more than 2-fold the hemicellulose and 1.5-fold pectin. Xylose and galacturonic acid were enriched in spines compared to fibers. The total lignin content in spines was 1.5-fold higher than those found in fibers, with elevated levels of syringyl (S) and guaiacyl (G) subunits but similar S/G ratios within tissues. Metabolomic profiling based on accurate mass spectrometry revealed the presence of phenolic compounds including quercetin, kaempferol, (+)-catechin, and (−)-epicatechin in A. fourcroydes spines, which were also detected in situ in spines tissues and could be implicated in the color of these plants’ structures. Abundance of (+)-catechins could also explain proanthocyanidins found in spines. Agave spines may become a plant model to obtain more insights about cellulose and lignin interactions and condensed tannin deposition, which is valuable knowledge for the bioenergy industry and development of naturally dyed fibers, respectively.