Boron deficiency energizes cyanide uptake and assimilation through activating plasma membrane H-ATPase in rice plants.

The effect of boron (B) deficiency on mediating the contribution of H-ATPase in the uptake and assimilation of exogenous cyanide (CN) is investigated. Under CN treatments, rice seedlings with B-deficient (-B) conditions exhibited significantly higher CN uptake and assimilation rates than B-supplemented (+B) seedlings, whereas NH uptake and assimilation rates were slightly higher in -B rice seedlings than in +B. In this connection, the expression pattern of genes encoding β-CAS, ST, and H-ATPase was assessed to unravel their role in the current scenario. The abundances of three β-CAS isogenes (OsCYS-D1, OsCYS-D2, and OsCYS-C1) in rice tissues are upregulated from both "CN-B" and "CN+B" treatments, however, only OsCYS-C1 in roots from the "CN-B" treatments was significantly upregulated than "CN+B" treatments. Expression patterns of ST-related genes (OsStr9, OsStr22, and OsStr23) are tissue specific, in which significantly higher upregulation of ST-related genes was observed in shoots from "CN-B" treatments than "CN+B" treatments. Expression pattern of 7 selected H-ATPase isogenes, OsA1, OSA2, OsA3, OsA4, OsA7, OsA8, and OsA9 are quite tissue specific between "CN+B" and "CN-B" treatments. Among these, OsA4 and OsA7 genes were highly activated in the uptake and assimilation of exogenous CN in -B nutrient solution. These results indicated that B deficiency disturbs the pattern of N cycles in CN-treated rice seedlings, where activation of ST during CN assimilation decreases the flux of the innate pool of NH produced from CN assimilation by the β-CAS pathway in plants. Collectively, the B deficiency increased the uptake and assimilation of exogenous CN through activating H-ATPase.