Abstract:
Proteases, including serine proteases, are involved in the entire life cycle of
plants. Proteases are controlled by protease inhibitors (PI) to limit any
uncontrolled or harmful protease activity. The role of PIs in biotic and abiotic
stress tolerance is well documented, however their role in various other plant
processes has not been fully elucidated. Seed development is one such area that
lack detailed work on the function of PIs despite the fact that this is a key process
in the life cycle of the plant. Serine protease inhibitors (SPI) such as the Bowman-
Birk inhibitors and Kunitz-type inhibitors, are abundant in legume seeds and act
as antinutrients in humans and animals. Their role in seed development is not
fully understood and present an interesting research target. Whether lowering
the levels and activity of PIs, in order to lower the anti-nutrient levels in seed will
affect the development of viable seed, remains an important question. Studies on
the function of SPI in seed development are therefore required. In this
Perspective paper, we provide an overview on the current knowledge of seed
storage proteins, their degradation as well as on the serine protease-SPI system
in seeds and what is known about the consequences when this system is
modified. We discuss areas that require investigation. This includes the
identification of seed specific SPIs; screening of germplasms, to identify plants
with low seed inhibitor content, establishing serine protease-SPI ratios and lastly
a focus on molecular techniques that can be used to modify seed SPI activity.
