How to only make one legend name italic in base R plot?

I want to add a legend to a plot in which only one of the legend names is italicized. I'm using plot() in base R.

• However, I need that italicized line to contain variable numbers, so I use bquote.

What I've tried does not work:

  a <- 2 ; b <- 5
  plot(a,b)
  l1 <- bquote(Italic ~ .(a) + .(b))
  l2 <- bquote(a + b)
  legend(x='topright',legend = bquote(italic(.(l1))))
  legend(x='topleft',legend = c(bquote(italic(.(l1))),l2))

• Notice that when I leave the expression on its own (RIGHT LEGEND), it italicizes correctly. However, when I add the text for other legend lines, it messes up (LEFT LEGEND).

How do I properly do this?

^{Note: I'd rather have a solution that doesn't require multiple calls to legend().}

You could use text.font = 3, say:

legend(x='topleft',legend = c(bquote((.(l1))),l2), text.font=c(3,1))