Study of soybean and lentil root exudates

Summary Some polyphenolic compounds have been identified in root exudates of two species of legumes (both cultivated in sterile conditions): for lentil, three desoxy-5 flavones (4′,7-dihydroxy, 3′,4′,7-trihydroxy and 4′,7-dihydroxy, 3′-methoxyflavones) and for soybean: two isoflavonoids, coumestrol and daidzein (or 4′,7-dihydroxyisoflavone). Identified compounds are polyphenolic aglycones whereas roots contain the corresponding glycosides, showing that a hydrolysis takes place at the time of exudation. Compounds are observed in plantlet exudates as soon as the first day after planting. Their daily quantitative variations parallel those of total phenolic compounds. Exudated coumestrol and 4′,7-dihydroxyflavone amounts are estimated at about 20% of root content in these molecules.     

A patatin-like protein with galactolipase activity is induced by drought stress in Vigna unguiculata leaves

This paper reports the cloning of a cDNA (Vupat1) expressed in Vigna unguiculata leaves coding for a protein with 48% sequence homology to patatin, the major protein from potato tuber which has lipolytic acylhydrolase activity. Two cultivars differing in drought tolerance were examined in Northern-blot analyses. Expression of Vupat1 is stimulated by drought stress, especially in the drought-sensitive cultivar. Vupat1 was expressed in the baculovirus system as a fusion protein secreted in the culture medium. The recombinant protein displays lipolytic activity towards monogalactosyldiacylglycerol, digalactosyldiacylglycerol and sulphoquinovosyldiacylglycerols.     

A novel patatin-like gene stimulated by drought stress encodes a galactolipid acyl hydrolase

A cDNA (Vupat1) encoding a predicted 43 kDa protein was isolated from drought-stressed cowpea (Vigna unguiculata) leaves. It has homology with patatin, a potato tuber storage protein with lipolytic acyl hydrolase activity. The recombinant protein VUPAT1 expressed in the baculovirus system displays preferentially galactolipid acyl hydrolase activity. Phospholipids are very slowly hydrolyzed and apparently triacylglycerols are not deacylated. Vupat1 promoter contains putative drought-inducible sequences. Northern blots showed that gene expression is stimulated by drought stress and is more pronounced in a drought-sensitive cultivar than in a drought-tolerant one. An involvement in drought-induced galactolipid degradation is proposed for VUPAT1.