Plant Physiol, April 2002, Vol. 128, pp. 1291-1302
Ocatin. A Novel Tuber Storage Protein from the Andean Tuber
Crop Oca with Antibacterial and Antifungal
Activities1
Teresita
Flores,
Alberto
Alape-Girón,
Marietta
Flores-Díaz, and
Hector E.
Flores*
Intercollege Graduate Program in Plant Physiology (T.F., H.E.F.)
and Department of Plant Pathology (H.E.F.), The Pennsylvania State
University, University Park, Pennsylvania 16802; and Departamento de
Bioquimica, Facultad de Medicina, Universidad de Costa Rica, San
José, Costa Rica (A.A.-G., M.F.-D.)
The most abundant soluble tuber protein from the Andean crop
oca (Oxalis tuberosa Mol.), named ocatin, has been
purified and characterized. Ocatin accounts for 40% to 60% of the
total soluble oca tuber proteins, has an apparent molecular mass
of 18 kD and an isoelectric point of 4.8. This protein appears to be
found only in tubers and is accumulated only within the cells of the pith and peridermis layers (peel) of the tuber as it develops. Ocatin
inhibits the growth of several phytopathogenic bacteria (Agrobacterium tumefaciens, Agrobacterium
radiobacter, Serratia marcescens, and
Pseudomonas aureofaciens) and fungi (Phytophthora cinnamomi, Fusarium oxysporum,
Rhizoctonia solani, and Nectria hematococcus). Ocatin displays substantial amino acid sequence similarity with a widely distributed group of intracellular
pathogenesis-related proteins with a hitherto unknown biological
function. Our results showed that ocatin serves as a storage protein,
has antimicrobial properties, and belongs to the Betv 1/PR-10/MLP
protein family. Our findings suggest that an ancient scaffolding
protein was recruited in the oca tuber to serve a storage function and
that proteins from the Betv 1/PR-10/MLP family might play a role in
natural resistance to pathogens.
1
This work was supported by a grant from the
McKnight Foundation.
*
Corresponding author; e-mail hef{at}psu.edu; fax 814-863-7217.
© 2002 American Society of Plant Physiologists
