Abstract

Salinity is a major constraint limiting global crop productivity. Salt-affected soil areas is rapidly expanding globally over recent decades due to the impacts of climate changes and human activities. Rice (Oryza sativa L.) is one of the most important stable crops that feed almost a half of the world’s population. However, rice is very sensitive to salinity stress and is currently listed as the most salt sensitive cereal crop with a threshold of 3 dSm⁻¹ for most cultivated varieties. Proline has been reported play an important role in abiotic stress tolerance in plants. Our previous investigation on proline-related gene expression patterns in wild and cultivated rice exposing to salinity stress indicated that wild rice O. australiensis plants accumulated proline by activating the genes related to proline synthesis, including OsP5CS1, OsP5CS2, and OsP5CR, and depressing proline degradation OsProDH gene at early as 1h after exposure to salt stress. Salt-sensitive cultivated rice Nipponbare, in contrast, upregulated the proline degradation gene OsProDH at the early stage of salt exposure (1h after salt treatment) and did not activate proline synthesis genes as early as it was in the wild rice. This research investigates whether editing (knock out) Proline dehydrogenase in rice cultivar Nipponbare (OsProDH) using CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats) could enhance salt tolerance in this cultivar. A total of 65 putative OsProDH edited Nipponbare rice lines were generated using Agrobacterium-mediated transformation of rice calli, 27 of them were confirmed OsProDH - edited by Sanger sequencing. These edited lines were evaluated for salinity tolerance using morphological and physiological assessments.  Results showed that different edited events resulted in different salt tolerant level in edited lines.