Walker, H. | Search bioRxiv

bioRxiv2022

A single amino acid transporter controls the uptake of priming-inducing beta-amino acids and the associated trade-off between induced resistance and plant growth.

Selected beta-amino acids, such as beta-aminobutyric acid (BABA) and R-beta-homoserine (RBH), can prime plants for resistance against broad-spectrum diseases. Here, we describe a genome-wide screen of fully annotated Arabidopsis T-DNA insertion lines for impaired in RBH-induced immunity (iri) against the downy mildew pathogen Hyaloperonospora arabidopsidis, yielding 104 lines that were partially affected and 4 lines that were completely impaired in RBH-induced resistance. The iri1-1 mutant phenotype could be confirmed by an independent T-DNA insertion in the same gene, encoding the high-affinity amino acid transporter LHT1. Using uptake experiments with IRI1/LHT1-expressing yeast cells and mass spectrometry-based quantification of RBH and BABA in leaves of mutant and over-expression lines of IRI1/LHT1, we demonstrate that IRI1/LHT1 acts as the main transporter for cellular uptake and systemic distribution of RBH and BABA. Subsequent characterisation of mutant and over-expression lines of IRI1/LHT1 for induced resistance and growth responses revealed that the level of IRI1/LHT1 expression determines the trade-off between induced resistance and plant growth by RBH and BABA.

plant biology↗

bioRxiv2021

The extracellular matrix promotes breast cancer cell growth under amino acid starvation by promoting tyrosine catabolism

Breast and pancreatic tumours are embedded in a collagen I-rich extracellular matrix (ECM) network, where nutrients are scarce due to limited blood flow and elevated tumour growth. Metabolic adaptation is required for cancer cells to endure these conditions. Here, we demonstrated that the presence of ECM supported the growth of invasive breast cancer cells, but not non-transformed mammary epithelial cells, and pancreatic cancer cells under amino acid starvation, through a mechanism that required macropinocytosis-dependent ECM uptake. Importantly, we showed that this behaviour was acquired during carcinoma progression. ECM internalisation, followed by lysosomal degradation, contributed to the upregulation of the intracellular levels of several amino acids, most notably tyrosine and phenylalanine. This resulted in elevated tyrosine catabolism on ECM under starvation, leading to increased fumarate levels, potentially feeding into the tricarboxylic acid cycle. Interestingly, this pathway was required for ECM-dependent cell growth under amino acid starvation, as the knockdown of p-hydroxyphenylpyruvate hydroxylase-like protein (HPDL), the third enzyme of the pathway, opposed cell growth on ECM in both 2D and 3D systems, without affecting cell proliferation on plastic. Finally, high HPDL expression correlated with poor prognosis in breast and pancreatic cancer patients. Collectively, our results highlight that the ECM in the tumour microenvironment represents an alternative source of nutrients to support cancer cell growth, by regulating phenylalanine and tyrosine metabolism.

cancer biology↗