ARAG1, an ABA-responsive DREB gene, plays a role in seed germination and drought tolerance of rice.
OBJECTIVE
DREB proteins are involved mainly in plant responses to abiotic stresses such as cold, drought or high salinity as well as ABA signalling. However, the function of most rice DREB genes and the underlying molecular mechanisms controlling these responses remains elusive. In this study, ARAG1, a rice DREB gene, was functionally analysed.


METHODS
Antisense and over-expression constructs of ARAG1 were introduced into rice by an Agrobacterium-mediated method. RT-PCR and western blot were used to detect ARAG1 accumulation in transgenics. PEG and ABA were used to test their response to abiotic stresses.


RESULTS
ARAG1 was expressed in inflorescences, roots, immature embryos and germinating seeds, but not in coleoptiles, leaves or mature embryos. Drought stress and ABA treatment increased transcript levels of the gene rapidly. ARAG1 knockdown line was hypersensitive to ABA application during seed germination and seedling growth. However, the line over-expressing ARAG1 behaved similarly to wild type in these circumstances. Knockdown of ARAG1 weakened tolerance of the transgenic seedlings to drought stress, while over-expression of it increased the tolerance slightly. In addition, activity of alpha-amylases was enhanced in germinating seeds of the knockdown and over-expression lines.


CONCLUSIONS
These results indicate that ARAG1 was involved in the ABA signalling and stress responsive pathways.
Zhao
Lifeng
L
Research Center for Molecular & Developmental Biology, Key Laboratory of Photosynthesis & Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Hu
Yibing
Y
Chong
Kang
K
Wang
Tai
T
D000222:Adaptation, Physiological / Q000502:physiology*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D055864:Droughts; D055785:Gene Knockdown Techniques; D017343:Genes, Plant; D018525:Germination / Q000502:physiology*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000502:physiology*
D029681:Arabidopsis Proteins; D017931:DNA Primers