Pontin/Reptin-associated complexes differentially impact plant development and viral pathology

Abstract

Pontin and Reptin are essential eukaryotic AAA+ ATPases that work together in several multiprotein complexes, contributing to chromatin remodeling and TARGET OF RAPAMCYIN (TOR) kinase complex assembly, among other functions. Null alleles of pontin or reptin are gametophyte lethal in plants, which has hindered studies of their crucial roles in plant biology. Here, we used virus-induced gene silencing (VIGS) to interrogate the functions of Pontin and Reptin in plant growth and physiology, focusing on Nicotiana benthamiana, a model species for the agriculturally significant Solanaceae family. Silencing either Pontin or Reptin caused pleiotropic developmental and physiological reprogramming, including aberrant leaf shape, reduced apical growth, delayed flowering, increased branching, chlorosis, and decreased spread of the RNA viruses Tobacco mosaic virus (TMV) and Potato virus X (PVX). To dissect these pleiotropic phenotypes, we took a comparative approach and silenced expression of key genes that encode subunits of each of the major Pontin/Reptin-associated chromatin remodeling or TOR complexes (INO80, SWR-C/PIE1, TIP60, TOR, and TELO2). We found that many of the pontin/reptin phenotypes could be attributed specifically to disruption of one of these complexes, with tip60 and tor knockdown plants each phenocopying a large subset of pontin/reptin phenotypes. We conclude that Pontin/Reptin complexes are crucial for proper plant development, physiology, and stress responses, highlighting the multifaceted roles these conserved enzymes have evolved in eukaryotic cells.

Amino Acid Signaling for TOR in Eukaryotes: Sensors, Transducers, and a Sustainable Agricultural fuTORe

“…This may be analogous to the mammalian model: TOR senses glycolytic intermediates (dihydroxyacetone phosphate), but only in cells that lack ATP-sensing pathways [93]. Although no ATP sensors are established in plant cells, a proposed ATP sensor for mammalian TOR, the cochaperone R2TP ATPase complex, is conserved in plants and regulates TOR activity, hinting that R2TP may be an ATP sensor in plant cells [94,95].…”