Arabidopsis tonoplast intrinsic protein and vacuolar H+-adenosinetriphosphatase reflect vacuole dynamics during development of syncytia induced by the beet cyst nematode Heterodera schachtii

Abstract

Plant parasitic cyst nematodes induce specific hypermetabolic syncytial nurse cell structures in host roots. A characteristic feature of syncytia is the lack of the central vacuole and the formation of numerous small and larger vesicles. We show that these structures are formed de novo via widening of ER cisternae during the entire development of syncytium, whereas in advanced stages of syncytium development, larger vacuoles are also formed via fusion of vesicles/tubules surrounding organelle-free pre-vacuole regions. Immunogold transmission electron microscopy of syncytia localised the vacuolar markers E subunit of vacuolar H-adenosinetriphosphatase (V-ATPase) complex and tonoplast intrinsic protein (γ-TIP1;1) mostly in membranes surrounding syncytial vesicles, thus indicating that these structures are vacuoles and that some of them have a lytic character. To study the function of syncytial vacuoles, changes in expression of AtVHA-B1, AtVHA-B2 and AtVHA-B3 (coding for isoforms of subunit B of V-ATPase), and TIP1;1 and TIP1;2 (coding for γ-TIP proteins) genes were analysed. RT-qPCR revealed significant downregulation of AtVHA-B2, TIP1;1 and TIP1;2 at the examined stages of syncytium development compared to uninfected roots. Expression of VHA-B1 and VHA-B3 decreased at 3 dpi but reached the level of control at 7 dpi. These results were confirmed for TIP1;1 by monitoring At-γ-TIP-YFP reporter construct expression. Infection test conducted on tip1;1 mutant plants showed formation of larger syncytia and higher numbers of females in comparison to wild-type plants indicating that reduced levels or lack of TIP1;1 protein promote nematode development.

Activity profiling of barley vacuolar processing enzymes provides new insights into the plant and cyst nematode interaction

“…However, the fact that we observed fluorescently labelled spherical structures with VPE activity close to the nematode’s head and in the apical region of the growing syncytia at 7 and 14 dpi cannot be ignored. Similar structures were observed by Baranowski et al () in syncytia induced by H. schachtii in A. thaliana roots. Some of these were considered to be lytic vacuoles and our results confirm these observations because the activity of legumains is inseparably associated with lytic vacuoles.…”

“…Thus, VPEs are considered as initiators of the vacuolar protein processing machinery (Hatsugai et al , ). Moreover, recently it has been shown that the organization of the vacuolar system in the syncytium induced by the beet cyst nematode H. schachtii in Arabidopsis thaliana roots changes dynamically during syncytium development, which indicates the importance of this cell compartment during plant–nematode interactions (Baranowski et al , ).…”

Profiling the Proteome of Cyst Nematode-Induced Syncytia on Tomato Roots

“…Caution is even more justified when subsequent regulatory levels are taken into account, e.g., post-translational modifications, subcellular localization, or substrate availability. In addition, the substantial number of detected proteome components involved in protein degradation, biosynthesis, and cellular trafficking processes supports not only the known enhancement of metabolic activity of syncytia, but also more recent findings on the role of autophagy and organellar de novo biogenesis during plant-nematode interactions [15,45].…”

Biocontrol efficacy of Bacillus velezensis strain YS-AT-DS1 against the root-knot nematode Meloidogyne incognita in tomato plants

“…Tonoplast intrinsic proteins (TIPs), localised in vacuoles, play a key role in plant defences against PPNs through the regulation of water and ion transport ( Baranowski et al, 2019 ). Therefore, three TIP genes ( TIP1.1 , TIP1.2 , TIP1.3 ), which displayed significant downregulation in the RKN-infected susceptible tomato roots ( Shukla et al, 2018 ), were selected to study the effects of Bv-DS 1 on their expression in the RKN-inoculated tomato roots.…”

“…The tonoplast intrinsic proteins (TIPs) have been described as the most abundant aquaporin proteins localized in the plant tonoplast ( Maurel et al, 2009 ) and play an important role in plant growth and development by regulating the transport of small substrates, such as water, glycerol, ammonia, H 2 O 2 , and urea ( Höfte et al, 1992 ; Gerbeau et al, 1999 ; Soto et al, 2008 ; Lindahl et al, 2018 ). TIPs have also been found to regulate plant responses to PPN infection ( Szakasits et al, 2009 ; Xue et al, 2013 ; Baranowski et al, 2019 ). In Arabidopsis , the feeding-site (syncytia) formation by cyst nematode is accompanied by reduced expression of several TIP genes ( Szakasits et al, 2009 ; Baranowski et al, 2019 ).…”