Chemical Imaging Reveals Diverse Functions of Tricarboxylic Acid Metabolites in Root Growth and Development

Abstract

Understanding how plants grow is critical for agriculture and fundamental for illuminating principles of multicellular development. Here, we apply chemical mapping of the developing maize root using desorption electrospray ionization mass spectrometry imaging (DESI-MSI). This technique reveals a range of small molecule distribution patterns across the gradient of stem cell differentiation in the root. To understand the developmental logic of these patterns, we examined tricarboxylic acid (TCA) cycle metabolites. In both Arabidopsis and maize, TCA metabolites are enriched in developmentally opposing regions, suggesting that stem-cell specific TCA metabolite localization may be conserved in evolutionarily divergent species. We find that these metabolites, particularly succinate, aconitate, citrate, and α-ketoglutarate, control root development in diverse and distinct ways. Critically, the effects of metabolites on stem cell behavior can be independent of their canonical role in ATP production. These results present new insights into development and suggest practical means for controlling plant growth.

Phase separation of S‐RNase promotes self‐incompatibility in Petunia hybrida

“…Furthermore, the redox state appears to modulate and balance S-RNase condensation or diffusion ability to ensure its optimal activity in self-incompatible pollen tubes, which is similar to the reversible formation of condensates by the Pbp1 LC domain, making the protein adapt cells to mitochondrial activity by H 2 O 2 -mediated oxidation (Kato et al, 2019). The H 2 O 2 levels in certain concentration ranges can promote root growth (Zhang et al, 2023) similar to our results, suggesting increasing H 2 O 2 contents promote growth under anaerobic or hypoxic survival conditions. This finding indicates that we can regulate the SRC formation in a switch-like pattern by altering the redox state to realize reversible conversion of self-pollen incompatibility and CPC.…”

Imaging plant metabolism in situ

“…Organic acids have important roles in plant physiology as central intermediates in carbon metabolism, pH regulation, and redox regulation ( Igamberdiev and Eprintsev, 2016 ), with many types having been spatially mapped in situ . For example, DESI-MSI of maize roots in longitudinal sections showed that tricarboxylic acid (TCA) cycle intermediates were enriched in developmentally distinct regions, with implications for plant growth and development ( T. Zhang et al , 2023 ). While succinate was enriched in the meristem, three TCA intermediates, aconitate, fumarate, and malate, were enriched in the differentiation zone.…”

“…Chemical data containing mass spectra at each tissue spot are then processed using specialized software to identify compounds, quantify their abundance, and generate spatial images. Five representative MSI studies are highlighted to illustrate spatial heterogeneity of metabolites: (top left) lipids in Arabidopsis thaliana seeds (graphical abstract, reprinted from Sturtevant et al , 2017 with permission from Elsevier), (bottom left) sugars, organic acids, and lipids in maize roots (modified from T. Zhang et al , 2023 ), (middle top) alkaloids in periwinkle petals [reproduced from Dutkiewicz et al (2021) , with permission], (middle bottom) vitamins in engineered tomato fruit (modified from Li et al , 2022 ), (right) lipid marker and Δ9-THCA in cannabis sugar leaves [reproduced from Lorensen et al (2023b) , with permission]. Additional details are described within the text and in corresponding articles.…”

How metabolism and development are intertwined in space and time

“…More large‐scale metabolite profiling indicates marked changes in several TCA cycle metabolites as cells transition from making primary walls to secondary cell walls (Li et al., 2016). More recently, the group of Alexandra Dickenson revealed via mass spectral imaging that intermediates of the TCA cycle appear to envoke distinctive developmental transitions which are independent of ATP levels (Zhang et al., 2023). A more direct link to cellulose synthesis is provided by sucrolytic activities.…”