Callose Deposition Is Responsible for Apoplastic Semipermeability of the Endosperm Envelope of Muskmelon Seeds1

Abstract

Semipermeable cell walls or apoplastic "membranes" have been hypothesized to be present in various plant tissues. Although often associated with suberized or lignified walls, the wall component that confers osmotic semipermeability is not known. In muskmelon (Cucumis melo L.) seeds, a thin, membranous endosperm completely encloses the embryo, creating a semipermeable apoplastic envelope. When dead muskmelon seeds are allowed to imbibe, solutes leaking from the embryo are retained within the envelope, resulting in osmotic water uptake and swelling called osmotic distention (OD). The endosperm envelope of muskmelon seeds stained with aniline blue, which is specific for callose (␤-1,3-glucan). Outside of the aniline-blue-stained layer was a Sudan III-and IVstaining (lipid-containing) layer. In young developing seeds 25 d after anthesis (DAA) that did not exhibit OD, the lipid layer was already present but callose had not been deposited. At 35 DAA, callose was detected as distinct vesicles or globules in the endosperm envelope. A thick callose layer was evident at 40 DAA, coinciding with development of the capacity for OD. Removal of the outer lipid layer by brief chloroform treatment resulted in more rapid water uptake by both viable and nonviable (boiled) seeds, but did not affect semipermeability of the endosperm envelope. The aniline-blue-staining layer was digested by ␤-1,3-glucanase, and these envelopes lost OD. Thus, apoplastic semipermeability of the muskmelon endosperm envelope is dependent on the deposition of a thick callose-containing layer outside of the endosperm cell walls.

Proteasome Inhibitors Affect Appressorium Formation and Pathogenicity of the Rice Blast Fungus, Magnaporthe oryzae

“…5B). It has been reported that callose deposition, which was detected by aniline blue and is induced by wounding stress or pathogen infection, was detected among the fungal infection patterns (Yim et al, 1998). The invading hyphae with serious branch spread were detected in infected leaves at 48 h with DMSO or PI treatment (Fig.…”

Developing Seeds of Arabidopsis Store Different Minerals in Two Types of Vacuoles and in the Endoplasmic Reticulum

“…In this context, the accumulation of callose in the chalazal cell wall (Figure 3) is puzzling, because this Glc polymer has been shown to restrain apoplast transport in seeds (Yim and Bradford, 1998). One possible explanation is that callose may function as a selective barrier to the transport of molecules into the endosperm from the surrounding maternal tissues.…”

Sensitivity of flowering plant gametophytes to temperature fluctuations

“…Callose deposition at the ovule chalazal end has been traditionally used as a microscopic feature to assess early ovule degeneration (Vishnyakova, 1991). Callose deposits play different functions in plant development and, although the function of callose has been interpreted traditionally to isolate dying from living cells, callose might also inhibit sugar transport to the aborting embryo sac (Sun et al, 2004) inasmuch as it limited the diffusion of small sugar molecules to the developing muskmelon (Cucumis melo L.) embryo (Yim and Bradford, 1998). Whether this is a cause or a consequence of female gametophyte degeneration is not known.…”