Abstract
The importance of the cuticular layer in regulating a plant’s water status and providing protection from environmental challenges has been recognized for a long time. The cuticular layer in plants restricts non-stomatal water loss and protects plants against damage from pathogen infection and UV radiation. Much genetic and biochemical research has been done about cutin and wax transportation in Arabidopsis thaliana, but little is known about it in rice. Here, we report that a rice ATP-binding cassette (ABC) transporter, OsABCG9, is essential for normal development during vegetative growth and could play a critical role in the transportation of epicuticular wax in rice. Rice phenotypes with mutated OsABCG9 exhibited growth retardation and sensitivity to low humidity. The total amount of cuticular wax on the leaves of the osabcg9-1 mutant diminished by 53% compared with the wild type, and wax crystals disappeared completely in osabcg9-2 mutant leaves. However, OsABCG9 does not seem to be involved in cutin transportation, even though its ortholog in Arabidopsis, AtABCG11, transports both wax and cutin. Furthermore, the osabcg9-1 mutant had increased leaf chlorophyll leaching and more severe drought susceptibility. This study provides new insights about differences between rice and A. thaliana in wax and cutin transportation associated with the ABCG family during evolution.
Highlights
To protect themselves from biotic and abiotic stress in the external environment, the outermost layer of the aerial organs of terrestrial plants are covered with a hydrophobic layer called the cuticle or cuticular membrane (Heredia, 2003)
We have shown that OsABCG9 gene is involved in wax accumulation in rice by analyzing two independent T-DNA insertional mutants
Family members close to OsABCG9 suggests that OsABCG9 plays roles in cuticular composition in epidermal tissues
Summary
To protect themselves from biotic and abiotic stress in the external environment, the outermost layer of the aerial organs of terrestrial plants are covered with a hydrophobic layer called the cuticle or cuticular membrane (Heredia, 2003). Cuticular wax and cutin are exported from epidermal cells to the cuticle, where they play essential roles in nonstomatal transpiration (Riederer and Schreiber, 2001) and protection against pathogenic microbes and herbivorous insects (Eigenbrode and Espelie, 1995) and UV exposure (Krauss et al, 1997). Because of those important protective functions, researchers are increasingly interested in the genes related to the cutin and wax pathways. Unlike AtABCG11, OsABCG9 plays an important function relating wax composition in rice
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