Distinct Lytic Vacuolar Compartments are Embedded Inside the Protein Storage Vacuole of Dry and Germinating Arabidopsis thaliana Seeds

Abstract

Plant cell vacuoles are diverse and dynamic structures. In particular, during seed germination, the protein storage vacuoles are rapidly replaced by a central lytic vacuole enabling rapid elongation of embryo cells. In this study, we investigate the dynamic remodeling of vacuolar compartments during Arabidopsis seed germination using immunocytochemistry with antibodies against tonoplast intrinsic protein (TIP) isoforms as well as proteins involved in nutrient mobilization and vacuolar acidification. Our results confirm the existence of a lytic compartment embedded in the protein storage vacuole of dry seeds, decorated by γ-TIP, the vacuolar proton pumping pyrophosphatase (V-PPase) and the metal transporter NRAMP4. They further indicate that this compartment disappears after stratification. It is then replaced by a newly formed lytic compartment, labeled by γ-TIP and V-PPase but not AtNRAMP4, which occupies a larger volume as germination progresses. Altogether, our results indicate the successive occurrence of two different lytic compartments in the protein storage vacuoles of germinating Arabidopsis cells. We propose that the first one corresponds to globoids specialized in mineral storage and the second one is at the origin of the central lytic vacuole in these cells.

Arabidopsis Seed Mitochondria Are Bioenergetically Active Immediately upon Imbibition and Specialize via Biogenesis in Preparation for Autotrophic Growth

“…To further investigate the subcellular location of this structure, we examined its localization with respect to PSVs, taking advantage of their specific autofluorescence (Bolte et al, 2011;Hunter et al, 2007;Fuji et al, 2007). In the dry seed, the PSVs were spherical to ovoid structures and filled much of the cell volume ( Figure 7; as previously described by Bolte et al [2011]). The spherical mitochondria were distributed seemingly randomly in the remaining cortical space and between the PSVs.…”

The relationship between vacuolation and initiation of PCD in rice (Oryza sativa) aleurone cells

“…There are two types of vacuoles in plant cells, i.e., PSVs and lytic vacuoles (LVs); the large central vacuole is a special type of LV456. PSVs mainly accumulate all kinds of proteins, such as defense proteins and storage proteins, as well as carbohydrates, etc.…”

Delivering of Proteins to the Plant Vacuole—An Update

“…Initially it was accepted that each type of vacuole was characterized by the type of aquaporin present in the tonoplast—tonoplast intrinsic proteins (TIPs): γ-TIP, lytic vacuole and α-TIP, protein storage vacuole [4,5]. However, the real situation can be much more complicated since overlap of both markers has been observed in vacuolar remodeling during transition between distinct types of vacuoles [6,7]. …”

“…However, this rearrangement of the vacuole seems to be related to the cell type, and eventually its specialization, since Olbrich and collaborators [6] observed that in meristematic cells a single vacuole type is formed initially presenting characteristics of both PSV and LV, that is gradually transformed into a central vacuole as the differentiation proceed. Recently, Bolte and colaborators [7] described the remodeling of Arabidopsis thaliana vacuome upon germination, illustrating the complexity of this system. Their results demonstrate a rapid and extreme reorganization of PSVs and LVs during early stages of seed germination, with the coexistence of two distinct compartments with very distinguishable roles.…”