Schlapfer, P. | bioRxiv Science

bioRxiv2022

Mutations in DNA polymerase δ subunit 1 mediate CMD2-type resistance to Cassava Mosaic Geminiviruses

Cassava mosaic disease suppresses cassava yields across the tropics. The dominant CMD2 locus confers resistance to the cassava mosaic geminiviruses. It has been reported that CMD2-type landraces lose resistance after regeneration through de novo morphogenesis. As full genome bisulfite sequencing failed to uncover an epigenetic mechanism for loss of resistance, we performed whole genome sequencing and genetic variant analysis and fine-mapped the CMD2 locus to a 190 kilobase interval. Data suggest that CMD2-type resistance is caused by a nonsynonymous, single nucleotide polymorphism in DNA polymerase {delta} subunit 1 (MePOLD1) located within this region. Virus-induced gene silencing of MePOLD1 in a Cassava mosaic disease-susceptible cassava variety produced a recovery phenotype typical of CMD2-type resistance. Analysis of other CMD2-type cassava varieties identified additional resistance alleles within MePOLD1. MePOLD1 resistance alleles represent important genetic resources for resistance breeding or genome editing, and elucidating mechanisms of resistance to geminiviruses.

plant biology↗

bioRxiv2020

Phosphate and phosphite differentially impact the proteome and phosphoproteome of Arabidopsis suspension cell cultures

Phosphorus absorbed in the form of phosphate (H2PO4-) is an essential but limiting macronutrient for plant growth and agricultural productivity. A comprehensive understanding of how plants respond to phosphate starvation is essential to develop more phosphate-efficient crops. Here we employed label-free proteomics and phosphoproteomics to quantify protein-level responses to 48 h of phosphate versus phosphite (H2PO3-) resupply to phosphate-deprived Arabidopsis thaliana suspension cells. Phosphite is similarly sensed, taken up, and transported by plant cells as phosphate, but cannot be metabolized or used as a nutrient. Phosphite is thus a useful tool to delineate between non-specific processes related to phosphate sensing and transport, and specific responses to phosphorus nutrition. We found that responses to phosphate versus phosphite resupply occurred mainly at the level of protein phosphorylation, complemented by limited changes in protein abundance, primarily in protein translation, phosphate transport and scavenging, and central metabolism proteins. Altered phosphorylation of proteins involved in core processes such as translation, RNA splicing, and kinase signalling were especially important. We also found differential phosphorylation in response to phosphate and phosphite in 69 proteins, including splicing factors, translation factors, the PHT1;4 phosphate transporter and the HAT1 histone acetyltransferase--potential phospho-switches signalling changes in phosphorus nutrition. Our study illuminates several new aspects of the phosphate-starvation response and identifies important targets for further investigation and potential crop improvement.

plant biology↗