Carbohydrates and carbohydrate enzymes in developing cotton ovules

Abstract

Hendrix, D. L. 1990. Carbohydrates and carbohydrate enzymes in developing cotton ovules. -Physioi. Plant. 78: 85-92.Patterns of carbohydrates and carbohydrate enzymes were investigated in developing cotton ovules to establish which of these might be related to sink strength in developing bolls. Enzymatic analysis of extracted tissue indicated that beginning 1 week following anthesis, immature cotton seeds {Gossypium hirsutum L. cv. Coker lOOA glandless) accumulated starch in the tissues which surround the embryo. Starting at 15 days post anthesis (DPA), this starch was depleted and starch simultaneously appeared in the embryo. Sucrose entering the tissues surrounding the embryo was rapidly degraded, apparently by sucrose synthase; the free hexose content of these tissues reached a peak at about 20 DPA. During the first few weeks of development these tissues contained substantial amounts of hexose but little sucrose; the reverse was true for cotton embryos. Embryo sucrose content rose sharply from the end of the first week until about 20 DPA; it then remained roughly constant during seed maturation. Galactinol synthase (EC 2.4.1.x) appeared in the embryos approximately 25 days after flowering. Subsequently, starch disappeared and the galactosides raffinose and stachyose appeared in the embryo. Except near maturity, sucrose synthase (EC 2.4.1.13) activity in the embryos predominated over that of both sucrose phosphate synthase (EC 2.4.1.14) and acid invertase (EC 3.2.1.26). Activities of the latter enzymes increased during the final stages of embryo maturation. The ratio of sucrose synthase to sucrose phosphate synthase was found to be high in young cotton embryos but the ratio reversed about 45 DPA. when developing ovules cease being assimilate sinks. Insoluble acid invertase was present in developing cotton embryos, but at very low activities; soluble acid invertase was present at significant activities only in nearly mature embryos. From these data it appears that sucrose synthase plays an important role in young cotton ovule carbohydrate partitioning and that sucrose phosphate synthase and the galactoside synthesizing enzymes assume the dominant roles in carbohydrate partitioning in nearly mature cotton seeds. Starch was found to be an important carbohydrate intermediate during the middle stages of cotton ovule development and raffinose and stachyose were found to be important carbohydrate pools in mature cotton seeds.

Reduced Oil Accumulation in Cottonseeds Transformed with aBrassicaNonfunctional Allele of a Delta‐12 Fatty Acid Desaturase (FAD2)

“…12). Sucrose, the principle form of carbon imported via the phloem (Tarczynski et al, 1992), was twice the level in Bnfad2 seeds than in null segregants, whereas levels of raffi nose, a prominent trisaccharide thought to function as a storage reserve and compatible solute (Hendrix, 1990), was not altered. Of the minor sugars, galactinol, the galactosyl donor for the synthesis of raffi nose and stachyose, was reduced in transgenic seeds, while trehalose glucose/galactose, fructose, and stachyose were unchanged.…”

High temperature limits in vivo pollen tube growth rates by altering diurnal carbohydrate balance in field-grown Gossypium hirsutum pistils

“…During the day, carbon export from the leaf is maintained by leaf sucrose pools through the activity of sucrose phosphate synthase (SPS), whereas export at night occurs via degradation of starch that accumulated during the preceding light period (Hendrix and Huber, 1986;Hendrix and Grange, 1991). Although some authors have reported changes in the carbohydrate balance of developing ovules during fiber development (Hendrix, 1990;Pettigrew, 2001), studies investigating the effect of high temperature on diurnal carbohydrate balance of the pistil on the day of anthesis are, to our knowledge, nonexistent.…”

“…Following extraction of soluble carbohydrates, starch was extracted from the pistil tissue pellet by adding 0.5 ml of 1 M KOH and placing the sample in a boiling water bath for approximately 1 h. Subsequently, starch was enzymatically hydrolyzed to glucose using methods previously described by Hendrix (1990). Following centrifugation at 10,000 × g for 15 min, the supernatant was brought to a final volume of 3 ml with distilled water.…”

“…The three supernatants were combined and brought to a final volume of 3 ml with 80% ethanol. Activated charcoal (30 mg) was added to each extract to remove any compounds that might interfere with the subsequent enzymatic analysis (Hendrix, 1990). After 5 min, samples were centrifuged at 10,000 × g for 15 min.…”

SuSy ergo GluSy: New Developments in the Field of Cellulose Biosynthesis

“…Whilst an involvement of sucrose synthase in providing substrates for cell wall biosynthesis is not an entirely novel idea (see for example Hendrix, 1990), this proposal has several advantages over previous concepts on cellulose biosynthesis. Firstly, by directly coupling UDP-GIc production and usage, the high free energy of sucrose hydrolysis can be used directly to drive glucan polymerization.…”