ИСТИНА

Fibrillarin is one of the major nucleolar proteins. In addition to its traditional function in methylation and processing of prerRNA, fibrillarin participates in virushost interactions in both animals and plants. To assess whether fibrillarin is also involved in other responses to biotic and abiotic stress, we generated potato plants (Solanum tuberosum cv. Chicago), which either transgenically overproduced fibrillarin or possessed markedly decreased levels of fibrillarin activity caused by virus (tobacco rattle virus, TRV) induced gene silencing (VIGS/RNAi). Heat stress (28O C) has been shown to strongly suppress plant growth and caused serious injuries such as leaf curling and senescence. Under such a heatstress condition, potato virus Y accumulates to markedly increased levels compared with normal temperature (22O C) and significantly aggravates these symptoms. Surprisingly, knockdown of fibrillarin achieved by TRVmediated VIGS notably attenuates these symptoms and suppresses the virus infection. In contrast, overproduction of fibrillarin in the overexpressing potato transgenic lines significantly accelerates all of these processes, suggesting involvement of fibrillarin in the responses of potato plants to heat stress combined or uncombined with potato virus Y infection. Thus, in this work we uncover completely new noncanonical function of fibrillarin in specific signaling pathways involved in abiotic and biotic stress. The possible molecular basis of fibrillarin effect and practical implications for control of virus infections will be discussed. This work was supported by Research Grant No. 14.W03.31.0003 from the Government of the Russian Federation.