Potato late blight is one of the destructive diseases in global agricultural production, which has the characteristics of rapid epidemic and rapid variation [1]. In the 19th century, the epidemic of Potato Late Blight in Europe once caused millions of people to starve to death, which was known as "Irish Famine", reflecting the profound impact of crop safety on human society [2]. At present, with many potato disease resistance genes being overcome by Phytophthora infestans, the global disease resistance gene resources are becoming increasingly scarce, so it is imperative to explore and protect broad-spectrum disease resistance genes [3,4].
Potato late blight (Yunnan, July 2017)
Recently, the crop disease team of Nanjing Agricultural University published a research paper on PNAs entitled "pathogen regulation of chloroplast function triggers a light dependent immune recognition" (direct submission), which cracked the molecular mechanism of the broad-spectrum disease resistance gene rpi-vnt1.1 of potato.
Rpi-vnt1.1 encodes the typical NLR (nucleus binding leucine rich repeat) receptor [5], which can activate the broad-spectrum resistance to late blight by recognizing the avrvnt1 effector protein secreted by late blight pathogen [6]. The potato varieties containing rpi-vnt1.1 have entered the North American market. However, the mechanism of rpi-vnt1.1 is not clear, which restricts the further development and utilization of the gene.
In this study, we first found that the function of rpi-vnt1.1 in recognizing Phytophthora infestans was light dependent. Then, we screened and identified glyk as the interacting protein of avrvnt1, which was the key factor for rpi-vnt1.1 to recognize avrvnt1. Furthermore, it was found that there was a light dependent alternative promoter selection (APS) regulatory mechanism in the glyk locus of potato, which could generate two transcripts, glykfl and glykcyt, under different light conditions. Among them, glykfl is the main transcript under light condition, and its product contains chloroplast signal peptide and distributes in chloroplast and maintains chloroplast function; while glykcyt accumulates continuously under dark condition, and it does not encode complete chloroplast signal peptide regulated by APS, so its product stays in cytoplasm, which is originally a shade response of plants [8]. Avrvnt1, a bacterial effector protein, targets the potato glykfl, which contains chloroplast signal peptide. By inhibiting glykfl from entering the chloroplast, it leads to plant susceptibility. Rpi-vnt1.1, a plant resistance gene, has been developed to recognize this behavior and activate the resistance, but the resistance is lost in the dark because avrvnt1 can not combine with glykcyt.
AVRvnt1/Rpi-vnt1.1–mediated HR and plant immunity is light-dependent（DD: 24 h dark；LD: 12 h light/12 h dark).
In conclusion, this study elucidated the mechanism of a broad-spectrum disease resistance gene with important agricultural value, revealed a typical case of light environment affecting plant resistance, and provided a new clue for green control of late blight in the context of global climate change.
It is reported that the communication unit of this paper is Nanjing Agricultural University. The first author is Gao chuyun, Ph.D., Professor Dong shameng, Professor Wang Yuanchao, Professor Sophien kamoun of Sainsbury Research Institute, Professor tolga Bozkurt of Imperial College of science and Engineering in London and other experts and their teams also participated in the study. The research was supported by the innovation group of NSFC, the general program and the graduate innovation project of Jiangsu Province.
Extended reading:
Nature communications | Nanjing Agricultural University team reveals the new mechanism of pathogen regulating host immunity
Genome biology | Nanjing Agricultural University analyzes the regulation mechanism of DNA methylation of plant oomycetes and the whole genome modification map
Reference
[1] Haverkort, A.J., Struik, P.C., Visser, R.G.F. et al. (2009) Applied Biotechnology to Combat Late Blight in Potato Caused by Phytophthora Infestans . Potato Res. 52, 249–264.
[2] Great Famine (Ireland). https://en.wikipedia.org/wiki/Great_Famine_(Ireland).
[3] Vleeshouwers VG, et al. (2011) Understanding and exploiting late blight resistance in the age of effectors. Annual review of phytopathology 49:507-531.
[4] Yoshida K, et al. (2013) The rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine. eLife 2:e00731.
[5] Foster SJ, et al. (2009) Rpi-vnt1.1, a Tm-2(2) homolog from Solanum venturii, confers resistance to potato late blight. Molecular plant-microbe interactions : MPMI 22(5):589-600.
[6] Pel MA (2010) Mapping, Isolation and characterization of genes responsible for Late Blight Resistance in Potato.
[7] Ridler. K. (2016). FDA gives OK for company's genetically engineered potato. The Washington Times.
[8] Ushijima T, et al. (2017) Light Controls Protein Localization through Phytochrome-Mediated Alternative Promoter Selection. Cell 171(6):1316-1325 e1312.
Paper link:
www.pnas.org/cgi/doi/10.1073/pnas.2002759117