Testa is involved in the control of storage mobilisation in seeds of Sesbania virgata (Cav.) Pers., a tropical legume tree from of the Atlantic Forest

Abstract

Seeds of Sesbania virgata (Cav.) Pers. (Leguminosae) contain galactomannan as a cell wall storage polysaccharide in the endosperm. After germination, it is hydrolysed by three enzymes: α-galactosidase (EC 3.2.1.22), endo-β-mannanase (EC 3.2.1.78) and β-mannosidase (EC 3.2.1.25). This work aimed at studying the role of the testa (seed coat) on galactomannan degradation during and after germination. Seeds were imbibed in water, with and without the testa, and used to evaluate the effect of this tissue on storage mobilisation, as well as its possible role in the galactomannan hydrolases activities. Immunocytochemistry and immunodotblots were used to follow biochemical events by detecting and localising endo-β-mannanase in different tissues of the seed. Endo-β-mannanase and α-galactosidase activities were found in the testa and latter in the endosperm during galactomannan degradation. The former enzyme was immunologically detected in the testa, mainly during germination. The absence of the testa during imbibition led to the anticipation of protein mobilisation and increased of the α-galactosidase activity and galactomannan degradation. Thus, the testa appears to play a role during storage mobilisation in the legume seed of S. virgata probably by participating in the control of the production, modification and/or storage of the hydrolases.

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

“…4a). The presence of proteins in the testa is very important, since this tissue is involved in the production, modification and/or storage of hydrolytic proteins, probably participating in the control (along with ABA) of the action of these hydrolases during and after germination (Tonini et al 2007).…”

“…In seeds of S. virgata, the testa appears to play a role during storage mobilisation, probably by participating in the control of the production, modification and/or storage of the hydrolases (Tonini et al 2007). Kontos and Spyropoulos (1996) suggested that the testa of carob controls the production of a-galactosidase and endo-b-mannanase in the endosperm of developing seeds.…”

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

“…In the endosperm and embryo, ABA increases as germination proceeds. The testa has cells that are metabolically active, with activities of a-galatosidase and endo-b-mannanase, and so it is possible that the high concentration of ABA negatively regulates storage mobilization before the embryo requires the sugars for growth (Tonini et al, 2007).…”

Catabolismo de sacarose durante a mobilização do galactomanano e sua importância na estratégia de sobrevivência de plântulas de Sesbania virgata (Cav.) Pers.

“…O processo de mobilização do galactomanano de sementes de Sesbania virgata é iniciado no segundo dia de embebição e atinge o seu máximo logo no terceiro dia. Após cinco dias do início da embebição, o endosperma já está completamente degradado e os cotilédones se desprendem da testa da semente (Tonini et al 2006(Tonini et al , 2007 e iniciam sua expansão, tornando-se órgãos fotossintéticos logo em seguida. Reid (1971) verifi cou um aumento nos teores de sacarose nos cotilédones de Trigonella foenumgraecum durante a mobilização do galactomanano e associou isso à absorção dos produtos de degradação do polissacarídeo.…”