A systematic comparison of embryogenic and non-embryogenic cells of banana (Musa spp. AAA): Ultrastructural, biochemical and cell wall component analyses

Abstract

Plant regeneration via somatic embryogenesis is essential for improvement of vegetatively propagated banana (Musa spp. AAA) through biotechnological techniques. A systematic comparison of embryogenic cells (ECs) and non-embryogenic cells (NECs) of banana was performed in the present study. Immuno-dot blotting, immunoflourescence labeling, biochemical and ultrastructural analyses were employed to study differences between ECs and NECs.Both immuno-dot analysis and immunofluorescence labeling revealed a higher abundance of fucosylated xyloglucans in cell walls of ECs. Arabinogalactan-protein (AGP) epitopes recognized by LM2 and NH4.3E5 antibodies were more abundant in NECs. On the other hand, AGPs recognized by JIM16, MAC204 and MAC207 antibodies were more abundant in ECs. Biochemical analyses revealed that the content of total soluble sugars and reducing sugars, as well as levels of indole-3-acetic acid, abscisic acid and zeatin riboside were significantly higher in ECs in comparison to NECs. In contrast, NECs showed significantly higher content of gibberellic acid. In addition, NECs were highly vacuolated and contained lipid bodies, prominent mitochondria and plastids, however, endoplasmic reticulum and Golgi bodies were not so abundant when compared to ECs.This study revealed that cell walls of ECs are rich in fucosylated xyloglucan and in AGP epitopes labeled by JIM16, MAC204 and MAC207 antibodies, indicating that these cell wall components together with higher levels of auxin, abscisic acid and zeatin riboside are contributing to the embryogenic competence of banana. In contrast, NECs showed more abundant non-fucosylated and non-XXXG xyloglucans in their cell walls, and higher level of gibberellic acid. This study provides new and useful information about hormonal and cell wall regulation of banana embryogenic competence which contributes to better understanding of this process, and might lead to practical applications in the near future.