The role of the OsCam1-1 salt stress sensor in ABA accumulation and salt tolerance in rice

Abstract

Involvement of the salt-inducible calmodulin gene, OsCam1-1, in abscisic acid (ABA) biosynthesis during salt stress was studied in the ‘Khoa Dawk Mali 105’ (KDML105) rice cultivar (Oryza sativa L.). FL530-IL, an isogenic salt-resistant line derived from the KDML105 cultivar, accumulated a 2.9-fold higher concentration of ABA in the leaves after salt stress treatment than that for KDML105. A twenty-four and a seven- fold higher level of OsCam1-1 transcripts were detected in the leaves of the FL530-IL and KDML105 rice cultivars, respectively, after 30 min of salt stress compared to non-salt-stressed plants. Transgenic rice lines that constitutively over-express the OsCam1-1 gene were found to up-regulate ABA aldehyde oxidase and 9-cis-epoxycarotenoid dioxygenase 3, two genes involved in ABA biosynthesis, and to have a higher ABA content, when compared to the wild type and the control transgenic lines without OsCam1-1 over-expression. In addition, transgenic plants over-expressing OsCam1-1 were more tolerant to salt stress, with, for example, a better ability to maintain their shoot and root mass (as dry weight) during salt stress, than the control plants. These data indicate that OsCam1-1 signaling is likely to play an important role in ABA biosynthesis, and the level of OsCam1-1 gene expression and ABA accumulation probably contribute to salt resistance in rice.