Cocultivating rye with berseem clover affects benzoxazinoid production and expression of related genes

Benzoxazinoids (BXs) are secondary metabolites synthesized mainly by gramineous plants, including rye (Secale cereale L.), that play an important role in stress resistance and allelopathy. In the present work, the influence of cocultivation of rye with berseem clover (Trifolium alexandrinum L.) on the expression of BX synthesis-regulating genes (ScBx1-ScBx5, ScIgl, and ScGT) and the content of six BXs (HBOA, DIBOA, GDIBOA, DIMBOA, GDIMBOA, and MBOA) in roots and the aerial portion of three rye inbred lines (ILs) (L318, D33, and D39) was investigated. Cocultivation of rye with berseem clover influenced its gene expression levels and BX contents. The response was strongly affected by rye genotype, plant part, time point, gene, and metabolite. The most frequently observed changes of gene expression concerned IL D33, aerial plant parts, the second time point (4 wk after germination), and ScBx3. For BX synthesis, the most frequently observed changes for IL D33 were in roots, the third time point (6 wk after germination), GDIBOA, and DIBOA. In 18.3% of cases, gene expression was correlated with BX synthesis. The coregulation of gene expression and BX synthesis in roots and aerial parts of rye plants affected by clover was observed relatively rarely. Cocultivation of rye with clover led, after 6 wk, to BX increases in roots of all tested ILs. Despite the lack of clearly universal response, the cocultivation of rye with clover may strengthen rye defense capability, at least against soil pathogens.