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9.B.308.  The Lettuce Infectious Yellows Virus P5 (LIYV-P5) Family 

The LIYV P5 protein is 39 aas long and has 1 TMS. It is part of the conserved quintuple gene block in the family Closteroviridae. The LIYV P5 protein is an endoplasmic reticulum (ER)-localized integral transmembrane protein. The knockout LIYV mutant presented reduced symptom severity and virus accumulation in Nicotiana benthamiana or lettuce plants, indicating its importance in efficient virus infection. P5, as well as its ortholog P6, encoded by Citrus tristeza virus (CTV) and another ER-localized protein encoded by LIYV RNA1, were found to cause cell death when expressed in N. benthamiana plants from a TMV vector, and it induced ER stress as well as the unfolded protein response (UPR) (Qiao et al. 2018). Several putative orthologues in different viruses are mentioned by Qiao et al. 2018, and these are presented in this family, although most of them show minimal sequence similarity.

References associated with 9.B.308 family:

Qiao, W., E.L. Helpio, and B.W. Falk. (2018). Two Crinivirus-Conserved Small Proteins, P5 and P9, Are Indispensable for Efficient Infectivity in Plants. Viruses 10:. 30154314