Sequence analysis of two new members of the major latex protein gene family supports the triploid-hybrid origin of the opium poppy.

Latex from the opium poppy (Papaver somniferum) contains an abundant group of laticifer-specific, low-molecular-weight polypeptides called the major latex proteins (MLPs). MLPs are encoded by a family of nine genes which can be divided into two distinct subfamilies based on DNA gel blot analysis. This report describes two new members of the MLP gene family (MLP146 and MLP149) that are physically linked and separated by approx. 5.5 kb. Comparison of their nucleotide and deduced amino-acid sequences with those of other MLP indicates that both new MLP belong to the MLP15 subfamily. The organization of the MLP family is consistent with the triploid-hybrid origin of the opium poppy.