Maturation Proteins and Sugars in Desiccation Tolerance of Developing Soybean Seeds

Abstract

The desiccation-tolerant state in seeds is associated with high levels of certain sugars and maturation proteins. The aim of this work was to evaluate the contributions of these components to desiccation tolerance in soybean (Glycine max [L.] Merrill cv Chippewa 64). When axes of immature seeds (34 d after flowering) were excised and gradually dried (6 d), desiccation tolerance was induced. By contrast, seeds held at high relative humidity for the same period were destroyed by desiccation. Maturation proteins rapidly accumulated in the axes whether the seeds were slowly dried or maintained at high relative humidity. During slow drying, sucrose content increased to five times the level present in the axes of seeds held at high relative humidity (128 versus 25 pg/axis, respectively). Stachyose content increased dramatically from barely detectable levels upon excision to 483 pg/axis during slow drying but did not increase significantly when seeds were incubated at high relative humidity. Galactinol was the only saccharide that accumulated to higher levels in axes from seeds incubated at high relative humidity relative to axes from seeds that were slowly dried. This suggests that slow drying serves to induce the accumulation of the raffinose series sugars at a point after galactinol biosynthesis. We conclude that stachyose plays an important role in conferring desiccation tolerance.The remarkable mechanism that allows most mature angiosperm seeds to survive desiccation to extremely low water contents is poorly understood. Among the protective components that have been proposed to be important in the acquisition of desiccation tolerance during seed development are proteins and soluble sugars. The group of proteins known as Late Embryogenesis Accumulating, or Lea (13), proteins include some that accumulate during the maturation drying phase of seed development. Some of these maturation proteins have been correlated with the ability of the seed to progress into seedling growth (29), whereas others have been correlated with desiccation tolerance (2, 4). However, some additional process is apparently necessary for the development of desiccation tolerance. We have shown that maturation protein accumulation alone is not sufficient to confer desiccation tolerance in developing soybean (4 characteristic of mature orthodox seeds (1). They have been implicated by correlation as adaptive agents for desiccation tolerance during seed development and germination (9,18,19). In particular, cultivars of soybean (Glycine max) accumulate high levels of the raffinose series of oligosaccharides, particularly stachyose, in addition to sucrose (12,18,21,31). Evidence for the protective role of soluble sugars has also been inferred from model systems (7, 11). The soluble sugar, trehalose, protects cytosolic components in yeast against desiccation-, frost-, and heat-induced damage in vivo (34). It is thought that the hydroxyl constituents of sugars may replace the hydration shell around membranes and thus prevent structural damage a...

Armazenabilidade de sementes de cafeeiro colhidas em diferentes estádios de maturação e submetidas a diferentes métodos de secagem

“…Estas proteínas, primeiramente descobertas em embriões de algodão, nomeadas proteínas lea, moduladas por ácido abscísico, acumulam em embriões de sementes de milho e cevada, durante os estádios mais tardios do desenvolvimento, em fase correspondente à aquisição de tolerância à dessecação (Bostock e Quatrano, citados por Leprince et al, 1993) e a sua expressão cessa rapidamente após a germinação (Blackman et al, 1991;Blackman et al, 1992). Segundo Thomann et al (1992) e Rosa et al (2004), proteínas lea também se acumulam em embriões de sementes de milho durante a lenta secagem, em fase correspondente à aquisição de tolerância à dessecação.…”

Reduced Sensitivity of <i>Campomanesia adamantium</i> (Cambess.) O. Berg Seeds to Desiccation: Effects of Polyethylene Glycol and Abscisic Acid

“…However, these proteins are not capable by themselves of promoting desiccation tolerance and, hence, maintaining seed viability [26].…”

Response of soybean genotypes to the expression of green seed under temperature and water stresses

“…The high green seed indices in the BRS 251 Robusta cultivar showed the susceptibility of the genotype, but some aspects should be considered, such as the difficulty in standardizing the development stages for the different cultivars and the smaller seed size of Robusta, that may have contributed to a premature classification of the R 6 stage and consequently greater stress effect. Several authors have reported difficulties in establishing precise identifications among the seed development stages and the irregularity of maturation among plants (Crookston and Hill, 1978;Blackman et al, 1992;Marcos Filho, 2005).…”