Factores que influyen en la embriogénesis somática in vitro de palmas (Arecaceae) / Factors affecting in vitro somatic embryogenesis of palms (Arecaceae)

La embriogénesis somática (ES) es una vía de desarrollo in vitro que presenta una serie de ventajas sobre otras técnicas utilizadas para la regeneración de palmas. Esta técnica tiene gran potencial para superar las limitaciones observadas al tratar de propagar clonalmente estas plantas utilizando yemas basales. A pesar de la conocida recalcitrancia que presentan las palmas al cultivo in vitro, si se utilizan los reguladores de crecimiento apropiados, el tipo y el estado de desarrollo del explante adecuados, así como genotipos con buena respuesta, es muy probable que se obtengan buenos resultados. Esto ha sido demostrado parcialmente en Phoenix dactylifera (palma dátil), Elaeis guineensis (palma aceitera), Bactris gasipaes (pejibaye) y Cocos nucifera (coco). También se ha logrado generar protocolos eficientes en otras palmas menos estudiadas, como Geonoma gamiova (una palma ornamental), Euterpe edulis (palmito dulce) y Areca catechu (palma de betel). La inducción de ES se ha conseguido principalmente con el uso de auxinas. De ellas, la que se ha utilizado con más frecuencia es el ácido 2,4-diclorofenoxiacético (2,4-D), aunque en algunos casos (como en pejibaye y palma aceitera) se ha usado picloram y dicamba, también con buenos resultados. Los explantes más utilizados han sido inflorescencias, ápices y segmentos basales de hojas, todos con un estado de desarrollo incipiente. También se ha visto que el tamaño del explante y el medio de cultivo juegan un papel importante en la respuesta. En este trabajo se presenta una recopilación de los trabajos más importantes sobre ES en esta familia de plantas y del efecto de varios factores sobre su establecimiento y desarrollo.

Somatic embryogenesis (SE) is an in vitro developmental pathway that exhibits a number of advantages over other techniques for regeneration of palms. This technique has great potential to overcome the limitations observed when trying to propagate these plants clonally using basal buds. Despite the known recalcitrance of palms for in vitro culture, good results can be obtained by using the appropriate growth regulators, explant type and developmental stage, as well as responsive genotypes. This has been partially observed in Phoenix dactylifera (date palm), Elaeis guineensis (African oil palm), Bactris gasipaes (peach palm) and Cocos nucifera (coconut). Efficient protocols have been also generated in less-studied palms, such as Geonoma gamiova (an ornamental palm), Euterpe edulis (Assai palm) and Areca catechu (areca palm). Induction of SE has been achieved mainly through the use of auxins. Of these, 2,4-dichlorophenoxyacetic acid (2,4-D) has been used most frequently, although in some cases (such as in peach palm and African oil palm) picloram and dicamba have been employed also with good results. The most commonly used explants are young inflorescences, apical buds and leaf-basal segments. Explant size and culture medium also play an important role in obtaining good results. This review presents a compilation of the most important publications on SE in this plant family and the effect of various factors on induction and development of this pathway.

Normalized embryoid cDNA library of oil palm (Elaeis guineensis) / Biblioteca ADNc normalizada de embrioides en aceite de palma (Elaeis guineensis)

A normalized embryoid cDNA library (EON) was constructed based on reassociation kinetics reaction. Results from dot blot hybridization and sequencing of EON cDNA clones clearly indicated that the normalization process reduced the frequency of high abundance transcripts and increased the frequency of low abundance gene transcripts. A total of 553 non-redundant expressed sequence tags (ESTs) were identified, 325 of these were not observed in the standard oil palm cDNA libraries sequenced previously. A total of 10 EON cDNA clones were chosen for expression profiling across samples from different stages of the tissue culture process. Two of the genes exhibited promising expression patterns for predicting the embryogenic potential in callus. Some of these genes were also differentially expressed in the various tissues of oil palm. This study showed that normalization of the existing embryoid library improved the chances of identifying transcripts not captured in the standard libraries, some of which could be associated with embryogenesis. This collection of ESTs is particularly well suited for use as candidate genes for development of an oil palm DNA chip, which can be used to obtain a more comprehensive view of the molecular mechanism associated with oil palm tissue culture.