Sweet sorghum (Sorghum bicolor L.) SbSTOP1 activates the transcription of a β-1,3-glucanase gene to reduce callose deposition under Al toxicity: A novel pathway for Al tolerance in plants

Abstract

Aluminum (Al) toxicity is a primary limiting factor for crop production in acid soils. Callose deposition, an early indicator and likely a contributor to Al toxicity, is induced rapidly in plant roots under Al stress. SbGlu1, encoding a β-1,3-glucanase for callose degradation, showed important roles in sorghum Al resistance, yet its regulatory mechanisms remain unclear. The STOP1 transcription factors mediate Al signal transduction in various plants. Here, we identified their homolog in sweet sorghum, SbSTOP1, transcriptionally activated the expression of SbGlu1. Moreover, the DNA sequence recognized by SbSTOP1 on the promoter of SbGlu1 lacked the reported cis-acting element. Complementation lines of Atstop1 with SbSTOP1 revealed enhanced transcription levels of SbGlu1 homologous gene and reduced callose accumulation in Arabidopsis. These results indicate, for the first time, that SbSTOP1 is involved in the modulation of callose deposition under Al stress via transcriptional regulation of a β-1,3-glucanase gene.