Pectin methylesterase (PME) inhibitor that inhibits PME in vitro. Functions as a critical structural modulator by regulating the degree of pectin methylesterification and the physiochemical properties of the cell wall components. Expressed in roots, leaves, culms and flag leaves. Induced by cold stress. Down-regulated by drought stress. Plants over-expressing PMEI28 are dwarf and have shortened culm length, due to increased level of pectin methylesterification. Belongs to the PMEI family. Truncated N-terminus.