Compromised function of ARM, the interactor of Arabidopsis telomerase, suggests its role in stress responses

Abstract

ARM was identified previously as an interaction partner of the telomerase protein subunit (TERT) in Arabidopsis thaliana. To investigate the interconnection between ARM and telomerase and to identify ARM cellular functions, we analyzed a set of arm mutant lines and arm/tert double mutants. Telomere length was not affected in arm single mutant plants, in contrast to double mutants. In the second generation of homozygous arm-1/tert double mutants following the heterozygous state during the double mutant construction, telomeres shortened dramatically, even below levels in tert plants displaying severe morphological defects. Intriguingly, homozygous arm-1/tert double mutants with short telomeres grew without obvious phenotypic changes for next two generations. Then, in agreement with the onset of phenotypic changes in tert, morphological defects were timed to the 5th arm-1/tert homozygous generation. RNAseq analyses of arm-1/tert and respective single mutants displayed markedly overlapping sets of differentially expressed genes in arm-1/tert double mutant and arm-1 single mutant lines, indicating a dominant effect of the ARM mutation. RNAseq data further implied ARM involvement in circadian rhythms, responses to drugs and to biotic and abiotic stimuli. In agreement with it, we observed sensitivity of arm-1 single mutant to the heat stress during germination. Altogether, our results suggest ARM involvement in crucial cellular processes without evidencing its role in the telomerase canonical function.