Abstract
Chloroplast is a crucial organelle for plant photosynthesis and maintaining normal life activities in higher plants. Although some genes related to chloroplast development and pigment synthesis have been identified or cloned in rice, little is known about the relationship between these genes and abiotic stress response. In this study, we identified a novel mutant white stripe leaf 12 (wsl12) affecting pigment synthesis, chloroplast development and abiotic stress response in rice. The mutant phenotype was obvious at seeding and tillering stages and in response to the temperature change. Genetic analysis of reciprocal crosses between wsl12 and wild-type plants showed that wsl12 was a recessive mutant in a single nuclear locus. Map-based cloning revealed that the WSL12 locus encoded OsNDPK2, one of the three nucleoside diphosphate kinases (OsNDPKs). WSL12 expressed in all tested tissues, while it highly expressed in leaves and young tissues. The WSL12 protein localized to the chloroplast. The wsl12 mutant showed higher superoxide anion level and enhanced sensitivity to abscisic acid (ABA) and salinity. The transcription pattern of many genes involved in chlorophyll biosynthesis, ABA synthesis, light signaling pathway, reactive oxygen species-scavenging pathway and the other two OsNDPKs was altered in the wsl12 mutant. These results indicate that the OsNDPK2 encoded by WSL12 plays an important role in chloroplast development and chlorophyll biosynthesis by regulating the expression levels of related genes. In addition, WSL12 also affects the response to abiotic stress, such as ABA and salinity in rice, and is beneficial to molecular breeding of stress tolerance.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-016-0479-6) contains supplementary material, which is available to authorized users.
Highlights
The transformation from proplastids to photosynthetically active chloroplasts is regulated by plastid and57 Page 2 of 15 nuclear genes
The transcription pattern of many genes involved in chlorophyll biosynthesis, abscisic acid (ABA) synthesis, light signaling pathway, reactive oxygen species-scavenging pathway and the other two OsNDPKs was altered in the wsl12 mutant. These results indicate that the OsNDPK2 encoded by WSL12 plays an important role in chloroplast development and chlorophyll biosynthesis by regulating the expression levels of related genes
Three types of leaves could be observed in the wsl12 mutant plants at tillering stage (Fig. 1c, e, f): Almost whole white leaf mainly distributed on the new leaves of new tillers (Fig. 1e), white stripe leaf and green leaf (Fig. 1f)
Summary
The mutants with abnormal pigment contents or deficient in chloroplast development are ideal materials for studying the underlying mechanisms that regulate chlorophyll biosynthesis and chloroplast development in rice. Many of these genes have been identified, including OsCHLH, Chlorina 1, Chlorina 9, V1, V2, V3, ST1, OsPPR1 and WSL (Jung et al 2003; Zhang et al 2006; Kusumi et al 2011; Sugimoto et al 2007; Yoo et al 2009; Gothandam et al 2005; Tan et al 2014). Wsl mutant, which suggests the function of WSL12 is pleiotropic
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