Hey Daniel,

Yes that totally looks like a lesion mimic slash constitutive defense/stress mutant.

The easiest first things you should try is check the temperature dependence, and the dependence on ammonium/nitrate ratio. See these papers:

http://www.ncbi.nlm.nih.gov/pubmed/23004358

http://www.ncbi.nlm.nih.gov/pubmed/20368979?report=abstract

Either regrow some at 28C (and 20-22 as control), or even switch some of the plants you have growing already, to see if they recover. This can give you fast ideas on the involvement of SNC1 and EDS1 etc.

Then try SA-measurement, I'd expect it to be high (hope you have access to GC-orLC-MS).

If you can rescue the dwarf phenotype at elevated temp, that will also allow you to make crosses to known defense mutants, to start doing some genetics.

You don't know what gene is mutated I assume?

Cool stuff! Goodluck,

Chris

btw if it's a TDNA line, you'll probably have heterozygotes too, use those for crosses to sid2 (SA dependent?), pad4.. etc etc. But if it's an ems mutant...goodluck getting flowers and seed on that poor little plant :-)

Oh yeah, almost forgot... how about disease resistance? Powdery mildew, Downy mildew, Pseudomonas? (expect higher resistance) or Botrytis, Alternaria? (expect lower resistance)

It certainly looks like a lesion mimic. You could also test the expression levels of PR genes to check if they are elevated as is typical of lesion mimic mutants. As Chris van Schie states you can also modify growing conditions as many lesion mimic phenotypes are conditional on certain environmental conditions. Perhaps try growing the plants at long and short days or at higher and lower light levels.

Looks interesting, good luck with it. Hope this helps?