Inositol Improves Cold Tolerance Through Inhibiting CBL1 and Increasing Ca(2+) Influx in Rapeseed (Brassica napus L.)

Rapeseed (Brassica napus L.) is an important oilseed crop worldwide. However, its productivity is significantly affected by various abiotic stresses, including cold stress. Among various stresses, cold stress is an important abiotic factor affecting plant growth, yield, and quality. The calcium channels are regarded as key pathways affecting cold tolerance in plants. Thus, improvement in cold tolerance is of great significance for crop improvement. The current study was designed to examine the beneficial role of exogenous inositol in improving cold stress tolerance in rapeseed. From the RNA-seq results, we identified 35 differently expressed genes encoding different inositol enzymes. The results show that inositol (a cyclic polyol) positively regulated cold tolerance by increasing calcium ion (Ca(2+)) influx in rapeseed. Furthermore, we found that the expression of calcineurin B-like (CBL1) gene was inhibited by inositol. On the other hand, overexpressed plant mediated the Ca(2+) flux under cold stress suggesting the key role of inositol-Ca(2+) pathway in cold tolerance. Moreover, the overexpression of BnCBL1-2 in Arabidopsis represented that transgenic plants mediated the Ca(2+) flux highlighting the vital role of the inositol-Ca(2+) pathway in conferring cold stress. Our study provides new insights into rapeseed cold tolerance mechanism and introduces a feasible method to improve the cold tolerance of rapeseed quickly.