Os09g0306400

OsbZIP71 encodes a rice bZIP TF, which plays an important role in the abscisic acid (ABA) signaling pathway of abiotic stress in plants.

Annotated Information

Function

Figure 1.Comparison of rice and Arabidopsis Group S bZIP proteins (a) and phylogenetic relationships among plant Group S1 bZIP members (b).(from reference ).

• OsbZIP71(LOC_Os09g13570) encodes a 154 amino acid protein. Amino acids 29–50 contain a typical bZIP basic region domain, and residues 51–112 contain a leucine zipper domain, which may also act as an active domain (Fig. 1a).
• The b-galactosidase activity of pBD71 showed no difference compared with the control construct, indicating that OsbZIP71 had no transactivation activity.
• The bZIP proteins are known to interact with G-box ciselement with an ACGT core sequence. The binding specificity of OsbZIP71 to the G-box element was determined using a one-hybrid system. results indicate that OsbZIP71 can function as a trans-acting factor for the G-box element, but the binding activity was not very high.
• Dimerization is one of the distinguishing characteristics of bZIP TFs. Liu et al. examined the dimerization activity of OsbZIP71 in vivo using a yeast two-hybrid system , showing that OsbZIP71 can form both homodimers as well as heterodimers with Group C proteins in yeast.
• It is proposed that: when plants encounter salt and drought stresses, OsbZIP71 is directly activated by the ABA-dependent pathway, and forms heterodimers with Group C members of the bZIP family or interacts with OsMyb4 to form a complex. These multi-protein complexes may then act together to bind promoters (containing G-box elements) of OsNHX1 and COR413-TM1, thereby enhances rice tolerance to drought and salt stresses.
• OsbZIP71 was strongly induced by ABA, and is involved in ABA sensitivity, which is an important aspect of the ABA-dependent regulation pathway. OsbZIP71 is associated with plant responses to low-oxygen stress.

GO assignment(s): GO:0005634, GO:0043565, GO:0046983

Mutation

• Two OsbZIP71-overexpressing lines (OE-16 and OE-19)
• two RNAi knockdown lines (RNAi-21 and RNAi-23)
• two inducible expression lines (IE-3 and IE-4)
• and wild type

They were used for germination tests. All transgenic lines were independent homozygous and single copy transgenic lines identified by Southern blot:
OsbZIP71 IE lines show insensitivity to ABA during seed germination.
OsbZIP71 RNAi seedlings show hypersensitivity to ABA.

Expression

• Liu et al. checked OsbZIP71 expression profile under different abiotic stresses:
  Realtime PCR analysis revealed that the transcript level of OsbZIP71 was strongly induced by drought, PEG, and ABA treatments, but repressed by salt.
  • OsbZIP71 was up-regulated more strongly in roots than in shoots following 6 h of PEG treatment.
  • In drought and ABA treated seedlings, OsbZIP71 expression was induced only in roots after the 0.5 and 4 h time-points, respectively.
  • In the salt treatments, OsbZIP71 was repressed both in shoots and roots within 0.5–6 h, and then restored to its basal expression level at 12 h.
  • OsbZIP71 was not changed at different time-points under normal condition, which suggesting that OsbZIP71 may function in abiotic stress signal transduction.
• those transgenic lines tolerance to salt and PEG osmotic stresses were positive correlated to relative expression of OsbZIP71 and

OsbZIP71 may regulate responses to salt and PEG osmotic stresses. OsbZIP71 overexpression significantly increased rice drought tolerance at both seedling and reproductive stages.

• In a word, Overexpression of OsbZIP71 enhanced drought and salt tolerance in rice. OsbZIP71 RNAi lines was sensitive to drought and salt stress in rice. Inducible expression of OsbZIP71 enhanced drought tolerance but sensitive to salt in rice.

Subcellular localization

To determine the subcellular localization of OsbZIP71, the ORF of OsbZIP71 was fused to GFP in the pA7-GFP vector OsbZIP71 is a nuclear-localized protein (Fig. 1d–f) and may function as a TF.

Evolution

NCBI BLASTp results also showed that OsbZIP71 was similar to Group S members of the Arabidopsis bZIP family, such as AtbZIP53, AtbZIP2/GBF5, AtbZIP44, and AtbZIP11/ATB2. Based on homology of the bZIP domains, the 16 members of rice Group S can be divided into three subgroups, designated S1, S2, and S3 (Fig. 1b). Further classification using MEGA4.0 with the known classified bZIP TFs indicated that OsbZIP71 belongs to Group S1 of the bZIP family(Fig. 1b)

Knowledge Extension

Figure 2.Summary of ABA signaling pathways that result in drought stress resistant responses.(from reference ).

• Unlike other cereal species, rice is able to germinate and elongate under anoxia. The regulatory mechanism that configures the transcriptome of rice during anaerobic germination is yet to be established. Although some rice varieties exhibit some

degree of tolerance to anaerobic stress that normally occurs during partial (hypoxia) or complete submergence (anoxia), it remains a major factor that limits productivity specially for the rainfed lowland cropping systems in Southeast Asia, where an average family relies on subsistence rice farming.

• The ability of rice to germinate under anoxia by extending the coleoptile is a highly unusual characteristic and a key feature underpinning the ability of rice seeds to establish in such a stressful environment. The process has been a focal point for research for many years. However, the molecular mechanisms underlying the anoxic growth of coleoptile still remain

largely unknown.

• Combined with recent findings on ABA signal transduction in Arabidopsis (Fig. 2), investigation into the genetic regulation of core ABA signal transduction components could promote the introduction of drought tolerance responses into various crop species. Since the identification of PYR/PYL/RCARs, a better understanding of signaling networks among the canonical ABA signaling components has shed light on the genetic modification of ABA signal transduction for improving drought tolerance in plants.
• OsbZIP71 is a member of anoxia stressed up-regulated transcription factors with potential significance to the pattern of cis-element enrichment among the upregulated genes.
• Major targets for this purpose include PYR/PYL/RCARs-PP2CSnRK2s complexes as well as their phosphorylation substrates

such as transcription factors or channel proteins. A PP2C binds to a SnRK2 in the absence of ABA and mediate dephosphorylation of the SnRK2 (Fig. 2). On the other hand, activation of SnRK2s as a critical positive signal for ABA signaling usually begins with autophosphorylation of SnRK2s.

Labs working on this gene

• State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
• State Key Laboratory of Hybrid Rice, Hunan Hybrid Rice Research Center, Changsha 410125, China
• National Center for Molecular Crop Design, Weiming Kaituo Agriculture Biotech Co., Ltd, Beijing 100085, China

Structured Information

Gene Name	Os09g0306400
Description	Eukaryotic transcription factor, DNA-binding domain containing protein
Version	NM_001069358.1 GI:115478455 GeneID:4346672
Length	2067 bp
Definition	Oryza sativa Japonica Group Os09g0306400, complete gene.
Source	Oryza sativa Japonica Group ORGANISM Oryza sativa Japonica Group Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta; Spermatophyta; Magnoliophyta; Liliopsida; Poales; Poaceae; BEP clade; Ehrhartoideae; Oryzeae; Oryza.
Chromosome	Chromosome 9
Location	Chromosome 9:8437301..8439367
Sequence Coding Region	8438089..8438268,8438686..8438967
Expression	GEO Profiles:Os09g0306400
Genome Context	<gbrowseImage1> name=NC_008402:8437301..8439367 source=RiceChromosome09 preset=GeneLocation </gbrowseImage1>
Gene Structure	<gbrowseImage2> name=NC_008402:8437301..8439367 source=RiceChromosome09 preset=GeneLocation </gbrowseImage2>
Coding Sequence	<cdnaseq>atgtcgagtgggacctcgtccgggtcgagccagggaacccggagctccaggtcggaagatgacctgaacctccaggcccagatggagaagaagaggaagaggaggaaggagtcgaaccgagagtcggctcggaggtctaggatgaggaagcaacagcacctcgacgaactcacctcgcaggtgaaccagctgaagaatcagaaccagcagctgagcatggcactgagcctgaccacacagaaccttgtggcagtgcaggcacagaactcagtgctgcaaacccaggagttggagctgcagagcaggctgtgtgccctaactgacatcctgatgtgcatgaacaacaccagtgctactcctactcctacaattccagccaccactacaagtgcttgtgatatttttggtgccagctcatggaaccagccacccatagacttgtaccagtaccagtgcttctga</cdnaseq>
Protein Sequence	<aaseq>MSSGTSSGSSQGTRSSRSEDDLNLQAQMEKKRKRRKESNRESAR RSRMRKQQHLDELTSQVNQLKNQNQQLSMALSLTTQNLVAVQAQNSVLQTQELELQSR LCALTDILMCMNNTSATPTPTIPATTTSACDIFGASSWNQPPIDLYQYQCF</aaseq>
Gene Sequence	<dnaseqindica>789..968#1386..1667#cccttttcccctcttccccagctcctttgttaggttttcttccagtgagctctttttgctcatattcagatcttcacttatttcctagttgttactactgcctttgagtattgacagcttcatcctgccaactcagctcaatcttcctctgaagtttcagtctttgtttctgaatctcttcagtgttcagaggggaagttctgccaaaaaatttctctggccatccattttccaaggggagattctgccaaaattttcatctctgtccatcaatattcctggggaggttctgccaaaattttctctgaaatcggttaatttataaggggaggttctgccgaaattttcgctggtcatcaatcttccctttgttgacataccctgcataagtatatacaacaaacatataactttttgcaaggtaagaaggagtttttatctgttcttgatgatagactcctagagaagttgtcctagttgtgtagatgttgttgctcatcatccctgagcacctcctctctagatttatgactggcccagccataacccagcttgttcagtccttctctgttgtcttcctctactggttctatgtcttctcagtaagctccctgtagttgtagccttttgaaattacaagacttatttatacaacataattatcaaggcatccacatataaactacaaggtatatatatatatatatatatatatttacaaaaagaaaaggaataagagggagtaaaattgttgccggtgcgaaaaaaaaaattgttgagaggtgaccatgtcgagtgggacctcgtccgggtcgagccagggaacccggagctccaggtcggaagatgacctgaacctccaggcccagatggagaagaagaggaagaggaggaaggagtcgaaccgagagtcggctcggaggtctaggatgaggaagcaacagcacctcgacgaactcacctcgcaggtttatatatatgctctgcttataatatatatatatatgtgcacaaaagtctaaagtttgtgatgcatacatagatctagtttattgtttttgctgtcataattgttttactttattttatctttatatgatagcttgcactcatgtgcaggtagaaagcaaaaaacagatgaaaacagaagtgccacttgaaatatctgccaaaaccaactcaataattgtgctgcctttttcaaaaggccccatcatctgtttcctacctaattcgttcaataacactagaaaacaattcatcatcatgatcttccttgtcataaattgagcactcaccaaactagcatcacaaccctgcatcaaaaatcaggaacagaagtctaaacacatatcactaagaaaatattatgtgtcactgaacaggtgaaccagctgaagaatcagaaccagcagctgagcatggcactgagcctgaccacacagaaccttgtggcagtgcaggcacagaactcagtgctgcaaacccaggagttggagctgcagagcaggctgtgtgccctaactgacatcctgatgtgcatgaacaacaccagtgctactcctactcctacaattccagccaccactacaagtgcttgtgatatttttggtgccagctcatggaaccagccacccatagacttgtaccagtaccagtgcttctgatctaggaataagaagagggttgttgtggtagtgtgggtaggaccagaagccatcaagtaatgtttcaatcatgtagggccattgttgtcactgttaatgtatgcaattcaatcttaattgcctgctgtaggggacagggatatttgctctttcttgtagctgttggtggtagagggattaccagatggcaaaatggtgctttggcaatgtgttaggtggggctggttttggttgttaagggtagggaggagaaaattggtaggtttttcttgagcatgcaagaggggaggcaaaggattttgtgtaatgatgctcttcaaggaaagtattcataattatgattataatgtaatatgtggatttggtggatcttcataggccaagtgcttctttgtgctcc</dnaseqindica>
External Link(s)	NCBI Gene:Os09g0306400, RefSeq:Os09g0306400