Intracellular Polyamines and Released Endochitinase EP3-like Proteins as Indicators of Embryogenic Potential of Musa spp. cvs. ‘Grande Naine’ (AAA) and ‘FHIA-18’ (AAAB) Cell Suspensions

The molecular characterization of embryogenic cultures helps us to understand the physiology of somatic embryogenesis and the events related to the occurring cell reprogramming and then to optimize protocols for this process. The present work seeks to contribute to these aims by biochemically defining embryogenic and non-embryogenic cell suspensions of two commercial bananas: Musa spp. cvs. ‘Grande Naine’ (AAA) and “FHIA-18” (AAAB). Thus, two types of putative biochemical indicators of embryogenic potential were studied: (i) major intracellular polyamines—1,3-diaminopropane (DAP), putrescine (Put), spermidine (Spd), and spermine (Spm)—taking into account their type of linkage with other molecules, and (ii) released endochitinase EP3-like proteins. Polyamine profiles of embryogenic and non-embryogenic cultures were analyzed using high-performance liquid chromatography (HPLC) with fluorescence detection, whereas immunoanalytical techniques (dot and Western blot) allowed the evaluation of the association of EP3-like proteins with different stages of somatic embryogenesis. The results indicated that polyamine contents and ratios discriminate the capacity for somatic embryogenesis and differentiation/proliferation status in cell suspensions. For example, the absence of Spm in the insoluble conjugate fraction of polyamines, lower Put contents (less than 1000 nmol per gram of fresh mass), and a lower free Put/Spm ratio (less than 1) were indicative of embryogenic cell suspensions when compared with those that were non-embryogenic and more proliferative. Furthermore, EP3-like proteins of banana were mainly released in highly embryogenic cultures. This supports the important role of EP3-like proteins in the viability of plants, since these enzymes are found to be related to somatic embryogenesis in a wide range of plant species.