Biology subjects

Torres-Montilla, S.

Publications and source records attributed to Torres-Montilla, S..

3 recordsLinked to original sources

bioRxiv2022

Novel insights on the contribution of plastoglobules and reactive oxygen species to chromoplast differentiation

Enriching plant tissues in phytonutrients can be done by stimulating their biosynthesis but also by providing appropriate sink structures for their sequestering and storage. Chromoplasts are plastids specialized in the production and accumulation of carotenoids that are naturally formed in non-photosynthetic tissues such as flower petals and ripe fruit. Chromoplasts can also be artificially differentiated from leaf chloroplasts by boosting the production of phytoene (the first committed intermediate of the carotenoid pathway) with the bacterial phytoene synthase crtB. Here we show that crtB-induced leaf chromoplasts develop plastoglobules harboring high levels of carotenoids (mainly phytoene and pro-vitamin A {beta}-carotene) but also other nutritionally-relevant isoprenoids such as tocopherols (vitamin E) and phylloquinone (vitamin K1). Further promoting plastoglobule proliferation by exposure to intense (high) light resulted in a higher accumulation of these health-related metabolites but also an acceleration of the chloroplast-to-chromoplast conversion. We further show that production of reactive oxygen species (ROS) stimulates chromoplastogenesis. Our data suggest that, similar to that already described for decreased photosynthesis and enhanced carotenoid biosynthesis, ROS production is not just a consequence but a promoter of the chromoplast differentiation process.

plant biology↗

bioRxiv2022

Chloroplast protein import determines plant proteostasis and retrograde signaling

Proteins containing polyglutamine (polyQ) repeats are prone to aggregation and can lead to distinct human pathologies. For instance, Huntingtons disease is caused by an abnormal expansion of the polyQ stretch (> Q35) of Huntingtin (HTT) protein. However, plants express hundreds of proteins containing polyQ regions, but no pathologies arising from these factors have been reported to date. Here, we ask how plants maintain the proteostasis of polyQ-containing proteins, which are intrinsically enriched in the plant proteomes. To this end, we overexpressed an aggregation-prone fragment of human HTT (Q69) in plant cells. In contrast to invertebrate and mammalian transgenic models, we find that Arabidopsis thaliana plants suppress Q69 aggregation. This elevated proteostasis ability is mediated through the import and degradation of Q69 in chloroplasts. Conversely, inhibition of chloroplast protein import either genetically or pharmacologically reduces the capacity of plant cells to prevent Q69 aggregation. We find that Q69 interacts with the chloroplast stromal processing peptidase (SPP). Notably, expression of synthetic Arabidopsis SPP is sufficient to suppress aggregation of polyQ-expanded HTT in human cells. Beyond ectopically expressed Q69-HTT, endogenous polyQ-containing proteins also aggregate in Arabidopsis upon inhibition of chloroplast import. Among them, the plastid casein kinase 2 (pCK2), which contains a polyQ region next to the chloroplast targeting sequence motif, can also be localized into the nucleus. Upon inhibition of chloroplast import, pCK2 accumulates at higher levels in the nucleus and forms diamond-shaped amyloid-like fibrils surrounding the chloroplasts. These results indicate that the differential conformation and redistribution of pCK2 to the nucleus depends on chloroplast import efficiency, providing a role of polyQ repeats in chloroplast to nucleus communication (i.e. retrograde signaling). Together, our findings establish chloroplast protein import and proteases as determinants of polyQ proteostasis, with important implications for plant biology that can also lead to therapeutic approaches for human diseases that involve protein aggregation.

plant biology↗

bioRxiv2021

The intrinsic chaperone network of Arabidopsis stem cells confers protection against proteotoxic stress

The biological purpose of plant stem cells is to maintain themselves while providing new pools of differentiated cells that form organs and rejuvenate or replace damaged tissues1-3. Protein homeostasis, or proteostasis, is required for cell function and viability4-7. However, the link between proteostasis and plant stem cell identity remains unknown. In contrast to their differentiated counterparts, we find that root stem cells can prevent the accumulation of aggregated proteins even under proteotoxic stress conditions such as heat stress or proteasome inhibition. Notably, root stem cells exhibit enhanced expression of distinct chaperones that maintain proteome integrity. Particularly, intrinsic high levels of the TRiC/CCT chaperonin determine stem cell maintenance and their remarkable ability to suppress protein aggregation. Overexpression of CCT8, a key activator of TRiC/CCT assembly8, is sufficient to ameliorate protein aggregation in differentiated cells and confer resistance to proteotoxic stress in plants. Taken together, our results indicate that enhanced proteostasis mechanisms in stem cells could be an important requirement for plants to persist under extreme environmental conditions and reach extreme long ages. Thus, proteostasis of stem cells could provide insights to design and breed plants tolerant to environmental challenges caused by the climate change.

plant biology↗