ABSTRACT

The ultraviolet B (UVB) sensitivity of rice cultivated in Asia and Africa varies greatly, with African rice cultivars (Oryza glaberrima Steud. and O. barthii A. Chev.) being more sensitive to UVB because of their low cyclobutane pyrimidine dimer (CPD) photolyase activity, which is a CPD repair enzyme, relative to Asian rice cultivars (O. sativa L.). Hence, the production of UVB-resistant African rice with augmented CPD photolyase activity is of great importance, although difficulty in transforming the African rice cultivars to this end has been reported. Here, we successfully produced overexpressing transgenic African rice with higher CPD photolyase activity by modifying media conditions for callus induction and regeneration using the parental line (PL), UVB-sensitive African rice TOG12380 (O. glaberrima). The overexpressing transgenic African rice carried a single copy of the CPD photolyase enzyme, with a 4.4-fold higher level of CPD photolyase transcripts and 2.6-fold higher activity than its PL counterpart. When the plants were grown for 21 days in a growth chamber under visible radiation or with supplementary various UVB radiation, the overexpressing transgenic plants have a significantly increased UVB resistance index compared to PL plants. These results strongly suggest that CPD photolyase remains an essential factor for tolerating UVB radiation stress in African rice. As a result, African rice cultivars with overexpressed CPD photolyase may survive better in tropical areas more prone to UVB radiation stress, including Africa. Collectively, our results provide strong evidence that CPD photolyase is a useful biotechnological tool for reducing UVB-induced growth inhibition in African rice crops of O. glaberrima.

摘要

亚洲和非洲种植的水稻对紫外线 B (UVB) 的敏感性差异很大，非洲水稻品种（Oryza glaberrima Steud. 和O. barthii A. Chev.）由于环丁烷嘧啶二聚体 (CPD) 较低，因此对 UVB 更敏感光解酶活性是一种 CPD 修复酶，相对于亚洲水稻品种 ( O. sativaL.)。因此，生产具有增强的 CPD 光解酶活性的抗 UVB 的非洲水稻非常重要，尽管据报道很难为此目的转化非洲水稻品种。在这里，我们通过使用亲本系 (PL)、UVB 敏感的非洲水稻 TOG12380 ( O. glaberrima）。过表达的转基因非洲水稻携带单拷贝 CPD 光解酶，其 CPD 光解酶转录物水平高 4.4 倍，活性比其 PL 对应物高 2.6 倍。当植物在生长室中在可见辐射或补充各种UVB辐射下生长21天时，与PL植物相比，过表达的转基因植物具有显着增加的UVB抗性指数。这些结果强烈表明，CPD 光解酶仍然是非洲水稻耐受 UVB 辐射胁迫的重要因素。因此，具有过表达 CPD 光解酶的非洲水稻品种可能在更容易受到 UVB 辐射胁迫的热带地区（包括非洲）生存得更好。集体，O. glaberrima。