Hemicelluloses of Cell Walls of a Proso Millet Cell Suspension Culture

Abstract

ABSTRACrCell wall composition of a stable suspension of proso millet (Panicum miliaceum L. cv Abarr) cells is similar to those of tissues and cell suspensions of other graminaceous species. Extraction of hemicelluloses with step-wise increasing concentrations of alkali yields materials that, like those of embryonal cells of maize coleoptiles, comprise mostly glucuronoarabinoxyla, xyloglucan, and small amounts of (1-3),(14)-f- MATERIALS AND METHODS Development of Cell Suspension Cultures. Embryogenic calli of proso millet (Panicum miliaceum L. cv Abarr) were obtained from mature seed (11) and were transferred monthly to LS medium (12) containing 2.5 mg/L 2,4-D, 4% (w/v) sucrose, and 0.8% (w/v) agar. About 1 g ofthe light yellow callus was dispersed into liquid medium in which LS medium was replaced by MS liquid medium (20; commercially packaged by GibCo) and 3% (w/v) sucrose. The suspension was initiated in 20 ml of medium in a 250-ml Erlenmeyer flask on a gyratory shaker at 100 cycles/ min with a 2.5 cm displacement. Ten ml of fresh medium was added three times at 4 to 5 d intervals, and after 2 weeks, 10 ml of the suspension was transferred with a sterile open-end pipet to 10 ml of fresh medium. The process was repeated for three culture cycles until the culture had stabilized. About 0.5 g of the cells was then transferred to 40 ml of fresh medium, and cells were subcultured biweekly. To yield suspensions of smaller cell colonies, a serological pipet was used to transfer cultures. Alternatively, small colonies that accumulated as a 'film' on the flask at or near the surface of the liquid medium were also collected and transferred to fresh medium. Both methods yielded stable cell suspensions that were maintained for 9 months before beginning these experiments. From observations by light microscopy,

Synthesis and Turnover of Cell-Wall Polysaccharides and Starch in Photosynthetic Soybean Suspension Cultures

“…Comparison of the data concerning label incorporation into the starch fraction and the actual starch content indicates that there was rapid turnover of starch in the SB-P and SB-M cells. Starch content of heterotrophically grown cells was much higher (5-14% of the cell dry weight, Carpita et al, 1985;Carpita and Kanabus, 1987), which also shows that there was a significant difference in carbohydrate metabolism between heterotrophic and photoautotrophic and mixotrophic cultured cells.…”

“…Similar changes in the 24% KOH-soluble and -insoluble fractions were described by Takeuchi and Komamine (1978) with heterotrophic V. Yosea suspension cultures. In proso millet cells, the hemicellulose proportion also increased during the culture period, whereas the pectin and strong acid-resistant cellulose fractions remained constant (Carpita et al, 1985). However, the pectin and cellulose fractions made up a smaller proportion of the cell wall because of an increase in hemicellulose, which is characteristic of cereal cell walls.…”

Synthesis of (1-->3), (1-->4)-beta-D-glucan in the Golgi apparatus of maize coleoptiles.

“…Not only must 3-and 4-linked glucosyl units be demonstrated, but the units must also be shown to be in the same polymer. Based on detection of 3-and 4-linked glucosyl units, Robinson and Glas (22) reported the synthesis of MG in microsomes obtained from cells that lack this glucan (23,24). Callose was undoubtedly formed, but a small amount of (1 -+ 4)-linked glucans may have arisen from another synthase activity related to the synthesis of xyloglucan.…”

Changes in Esterification of the Uronic Acid Groups of Cell Wall Polysaccharides during Elongation of Maize Coleoptiles

“…8), similar to the pectins of a proso millet cell culture (6,9). Fraction I comprised an association of PGA with GAX and type II arabinogalactan(protein)s and fraction II enriched in PGA and RG with associated arabinans and type I arabinogalactan(protein)s (6).…”