The distribution of hydroxyproline‐rich glycoprotein mRNAs in shoots of cucumber and pea

Abstract

The distribution of hydroxyproline‐rich glycoprotein (HRGP) mRNAs in the shoots of dark‐grown and irradiated cucumber (Cucumis sativus L. cv. Burpee pickler) and pea (Pisum sativum L. cv. Alaska) was studied. A cloned genomic DNA fragment encoding carrot (Daucus carota) root extensin (pDC5A1) was used to measure HRGP mRNAs from cucumber and pea along the length of dark‐grown and irradiated shoots. There was a marked difference in the levels of HRGP mRNAs isolated from apical and basal regions of cucumber. Whereas apical, elongating regions had low levels of HRGP mRNAs, basal regions of the shoot had high levels. Levels of HRGP mRNAs were also compared in shoots of dark‐grown and irradiated cucumber. Although light inhibits hypocotyl growth, it had no effect on levels of HRGP mRNAs. There was no gradient in the distribution of HRGP mRNAs along the epicotyl of dark‐grown pea. As was the case with cucumber, light did not affect the accumulation of HRGP mRNAs in pea shoots. We conclude that light does not affect elongation by regulating the accumulation of HRGP mRNAs. The gradient of accumulation of HRGP mRNAs along the hypocotyl of cucumber probably reflects differences in cellular differentiation along the shoot.