Roles of Yieldin and Expansin on Cowpea Wall Extension

Abstract

Wall-yielding properties have been described with Lockhart's wall parameters (extensibility and yield tension) determined by fitting the stress-extension rate curves with two linear regression lines. These two parameters are regulated pH-dependently in the elongation growth. It has been reported that yieldin from cowpea (Vigna unguiculata L.) hypocotyls does not regulates extensibility but yield tension. On the other hand, we have recently demonstrated that cucumber expansin (CsEXPA1) is capable of regulating both wall parameters.
To clarify the roles of yieldin and expansin on the wall extension, we obtained both yieldin (VuYLD1) and expansin (VuEXPA1) from the cell wall of cowpea hypocotyls and examined the function of VuYLD1 and VuEXPA1 using the isolated wall preparation of cowpea hypocotyl. We show that VuEXPA1 also regulates both extensibility and yield tension by reconstitution assays. The function of VuYLD1 will also be shown.