# The paralogous R3 MYB proteins CAPRICE, TRIPTYCHON and ENHANCER OF TRY AND CPC1 play pleiotropic and partly non-redundant roles in the phosphate starvation response of Arabidopsis roots

## TL;DR

This study shows how three related R3 MYB proteins in Arabidopsis roots help plants respond to low phosphate levels by regulating various genes and processes.

## Contribution

The paper reveals new functions of R3 MYB proteins in phosphate starvation response and challenges the concept of genetic redundancy.

## Key findings

- Three R3 MYB proteins regulate root hair development and phosphate starvation response.
- Phosphate deficiency induces new roles in metal transport and membrane lipid remodelling.
- Environmental changes can assign unique functions to otherwise redundant proteins.

## Abstract

RNA sequencing of mutants defective in the expression of three paralogous MYB transcription factors revealed pleiotropic roles and dynamic shifts in the function of the proteins upon exposure to phosphate starvation.

Phosphate (Pi) deficiency alters root hair length and frequency as a means of increasing the absorptive surface area of roots. Three partly redundant single R3 MYB proteins, CAPRICE (CPC), ENHANCER OF TRY AND CPC1 (ETC1) and TRIPTYCHON (TRY), positively regulate the root hair cell fate by participating in a lateral inhibition mechanism. To identify putative targets and processes that are controlled by these three transcription factors (TFs), we conducted transcriptional profiling of roots from Arabidopsis thaliana wild-type plants, and cpc, etc1 and try mutants grown under Pi-replete and Pi-deficient conditions using RNA-seq. The data show that in an intricate interplay between the three MYBs regulate several developmental, physiological and metabolic processes that are putatively located in different tissues. When grown on media with a low Pi concentration, all three TFs acquire additional functions that are related to the Pi starvation response, including transition metal transport, membrane lipid remodelling, and the acquisition, uptake and storage of Pi. Control of gene activity is partly mediated through the regulation of potential antisense transcripts. The current dataset extends the known functions of R3 MYB proteins, provides a suite of novel candidates with critical function in root hair development under both control and Pi-deficient conditions, and challenges the definition of genetic redundancy by demonstrating that environmental perturbations may confer specific functions to orthologous proteins that could have similar roles under control conditions.