Storage proteins and cell wall mobilisation in seeds of Sesbania virgata (Cav.) Pers. (Leguminosae)

Abstract

The endosperm of seeds of Sesbania virgata (Cav.) Pers. accumulates galactomannan as a cell wall storage polysaccharide. It is hydrolysed by three enzymes, one of them being a-galactosidase. A great amount of protein bodies is found in the cytoplasm of endospermic cells, which are thought to play the major role as a nitrogen reserve in this seed. The present work aimed at understanding how the production of enzymes that degrade storage compounds is controlled. We performed experiments with addition of inhibitors of transcription (actinomycin-D and a-amanitin) and translation (cycloheximide) during and after germination. In order to follow the performance of storage mobilisation, we measured fresh mass, protein contents and a-galactosidase activity. All the inhibitors tested had little effect on seed germination and seedling development. Actinomycin-D and cycloheximide provoked a slight inhibition of the storage protein degradation and concomitantly lead to an elevation of the a-galactosidase activity. Although a-amanitin showed some effect on seedling development at latter stages, it presented the former effect and did not change galactomannan degradation performance. Our data suggest that some of the proteases may be synthesised de novo, whereas a-galactosidase seems to be present in the endosperm cells probably as an inactive polypeptide in the protein bodies, being probably activated by proteolysis when the latter organelle is disassembled. These evidences suggest the existence of a connection between storage proteins and carbohydrates mobilisation in seeds of S. virgata, which would play a role by assuring a balanced afflux of the carbon and nitrogen to the seedling development.

Haustorium–endosperm relationships and the integration between developmental pathways during reserve mobilization in Butia capitata (Arecaceae) seeds

“…are known to induce carbohydrate mobilization in legume seeds (Brandão et al, 2009), and CKs likewise increase proteolytic activities and carbohydrate and lipid mobilization (Bewley et al, 2013). There is also evidence that ethylene induces galactomannan mobilization (Tonini et al, 2010) and the accumulation of ROS (which signal in the programmed cell death pathway) (Bailly, 2004;Gadjev et al, 2008;Gomes et al, 2014;Wojtyla et al, 2016). We observed that these processes resulted in the mobilization of cell wall carbohydrates, extravasation of cellular contents, and the extension of the range of collapsed cells in the adjacent endosperm of germinated B. capitata seeds.…”

Seed Cell Wall Storage Polysaccharides: Models to Understand Cell Wall Biosynthesis and Degradation

“…However, when seeds of S. virgata were incubated with a-amanitin, actinomycin-D, and cyclohehimide, different results were obtained (Tonini et al, 2010a), suggesting that the enzymes necessary for galactomannan degradation are already present, possibly in protein bodies. As storage protein degra-dation occurs, the hydrolases are released to the storage cell wall.…”

Effects of abscisic acid, ethylene and sugars on the mobilization of storage proteins and carbohydrates in seeds of the tropical tree Sesbania virgata (Leguminosae)

“…The inhibitory effect of ABA during the degradation of proteins, mainly at the beginning of storage mobilization, can be related to the de novo synthesis of proteases and/or activation of the pre-formed proteases, as observed in seeds of barley (Hordeum vulgare) (Cercos et al, 1999), apple (Malus domestica) (Ranjan and Lewak, 1995), rice (Shintani et al, 1997) and bean (Phaseolus vulgaris) (Domash et al, 2006). Thus, it is likely that protein and carbohydrate metabolism might be linked to each other through their own catalytic processes so that the production and delivery of compounds related to carbon and nitrogen metabolism would be balanced during seedling development (Tonini et al, 2010).…”