Ferritin accumulation and degradation in different organs of pea (Pisum sativum) during development

Abstract

Iron concentration and ferritin distribution have been determined in different organs of pea (Pisum sativum) during development under conditions of continuous iron supply from hydroponic cultures. No ferritin was detected in total protein extracts from roots or leaves. However, a transient iron accumulation in the roots, which corresponds to an increase in iron uptake, was observed when young fruits started to develop. Ferritin was detectable in total protein extracts of flowers and pods, and it accumulated in seeds. In seeds, the same relative amount of ferritin was detected in cotyledons and in the embryo axis. In cotyledons, ferritin and iron concentration decrease progressively during the first week of germination. Ferritin in the embryo axis was processed, and disappeared, during germination, within the first 4 days of radicle and epicotyl growth. This degradation of ferritin in vivo was marked by a shortening of a 28 kDa subunit, giving 26.5 and 25 kDa polypeptides, reminiscent of the radical damage occurring in pea seed ferritin during iron exchange in vitro [Laulhere, Laboure & Briat (1989) J. Biol. Chem. 264, 3629-3635]. Developmental control of iron concentration and ferritin distribution in different organs of pea is discussed.

Sustained growth promotion in Arabidopsis with long-term exposure to the beneficial soil bacteriumBacillus subtilis(GB03)

“…The iron concentration in leaves was determined as described previously. 27 Tissue of 100-200 mg was ground with liquid N 2 and mineralized according to Beinert. 28 Iron concentration was measured by absorbance of Fe 2+ -O-phenanthroline at 510 nm at pH 6.0 using thioglycolic acid as a reducing agent.…”

Proteomics of the Chloroplast: Systematic Identification and Targeting Analysis of Lumenal and Peripheral Thylakoid Proteins

“…Ferritin concentrates and stores cellular iron to ‫01ف‬ 11 times the solubility of the free ion and earlier had been determined to be a plastid protein located at the stromal side of thylakoid membranes (e.g., Waldo et al, 1995). Ferritin accumulation is positively correlated to iron loading of the plant, is regulated at a transcriptional level (Gaymard et al, 1996), and is under developmental control (Lobreaux and Briat, 1991). The FKBP isomerase is only the second isomerase identified in the thylakoid; the other one was named TLP40 (Fulgosi et al, 1998).…”

Ferritin is required for rapid remodeling of the photosynthetic apparatus and minimizes photo‐oxidative stress in response to iron availability in Chlamydomonas reinhardtii

“…In mammals, its regulation mainly takes place at the level of translation via the suppressor proteins IRP1 and IRP2, which control the binding of ribosomes to the ferritin mRNA (Thomson et al, 1999), whereas plant ferritin is mainly regulated at the transcription level . During the early stages of plant development, ferritin is mostly detected in the non-green plastids of seeds and developing organs, such as young leaves, where it serves as an iron pool (Lobreaux and Briat, 1991), whereas in the chloroplasts it is only found during senescence (Buchanan-Wollaston and Ainsworth, 1997;Seckback, 1982). Tobacco plants overexpressing ferritin showed that careful ferritin level adjustments are necessary.…”