Spatial and temporal distribution of the major isoforms of puroindolines (puroindoline-a and puroindoline-b) and non specific lipid transfer protein (ns-LTPle1) of Triticum aestivum seeds.: Relationships with their in vitro antifungal properties

In wheat endosperm, the main isoforms of puroindolines (PIN-a and PIN-b) and nonspecific lipid transfer protein (ns-LTP1e(1)), structurally related lipid binding proteins, were asynchronously synthesized during maturation and are partially degraded during germination. These proteins are not detected in roots and hypocotyls of seedlings, while ns-LTP1e(1), but not PINs, was synthesized during germination in the scutellum and/or mesocotyl. In mature wheat seeds, ns-LTP1-e(1) was specifically localised within aleurone cells but not in cell walls in marked contrast with most other plant ns-LTP1s. PINs are both located in the starchy endosperm and in the aleurone layer. In the latter cells, PINs and ns-LTP1-e(1) were both localised in small inclusions within protein-rich aleurone grains. In the mature starchy endosperm, PINs were localised in the protein matrix and at the interface between starch granules and protein matrix. It was shown that both PIN-a and PIN-b, have antifungal properties in vitro and a synergistic enhancement of the antifungal properties of alpha-purothionins (alpha-PTH) was observed in the presence of PINs. This synergism could have biological significance since alpha-PTH and PINs are both located in the protein matrix of starchy endosperm. ns-LTP1e(1) is not capable to inhibit growth of fungi and a synergy rather weak in comparison with PINs was also observed between ns-LTP1e(1) and alpha-PTH. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.