Chromatin-remodeling factor OsINO80 is involved in regulation of gibberellin biosynthesis and is crucial for rice plant growth and development

The phytohormone gibberellin（GA） plays essential roles in plant growth and development. Here,we report that OsINO80, a conserved ATP-dependent chromatin-remodeling factor in rice（Oryza sativa）, functions in both GA biosynthesis and diverse biological processes. OsINO80-knockdown mutants, derived from either T-DNA insertion or RNA interference, display typical GA-deficient phenotypes, including dwarfism, reduced cell length, late flowering, retarded seed germination and impaired reproductive development. Consistently, transcriptome analyses reveal that OsINO80 knockdown results in downregulation by more than two-fold of over 1,000 genes, including the GA biosynthesis genes CPS_1 and GA_3ox_2, and the dwarf phenotype of OsINO80-knockdown mutants can be rescued by the application of exogenous GA3. Chromatin immunoprecipitation（Ch IP） experiments show that OsINO80 directly binds to the chromatin of CPS1 and GA_3ox_2 loci. Biochemical assays establish that OsINO80 specially interacts with histone variant H_2A.Z and the H_2A.Z enrichments at CPS_1 and GA_3ox_2 are decreased in OsINO80-knockdown mutants. Thus, our study identified a rice chromatin-remodeling factor,OsINO80, and demonstrated that OsINO80 is involved in regulation of the GA biosynthesis pathway and plays critical functions for many aspects of rice plant growth and development.

OsbZIP01 Affects Plant Growth and Development by Regulating OsSD1 in Rice

As the‘Green Revolution’gene,SD1(encoding GA20ox2),has been widely applied to improve yield in rice breeding.However,research on its transcriptional regulation is limited.Here,we identified a transcription factor OsbZIP01,which can suppress the expression of SD1 and regulate gibberellin(GA)biosynthesis in rice.Knockout mutants of OsbZIP01 exhibited increased plant height,while the overexpression lines showed a semi-dwarf phenotype and diminished germination rate.Furthermore,the semi-dwarf phenotype of OE-bZIP01,was caused by the reduced internode length,which was accompanied by a thin stem width.The predominant expression of OsbZIP01 was observed in leaves and sheaths.OsbZIP01 protein was localized in the nucleus and showed transcriptional repression activity.In addition,OsbZIP01 could directly bind to the promoter of the OsSD1 gene,and inhibit its transcription.The semi-dwarf phenotype of OE-bZIP01 could be rescued by exogenous GA_(3).Meanwhile,the bzip01 sd1 double mutant showed a shorter shoot length compared with the wild type,indicating that OsbZIP01 regulated plant growth mainly through the GA biosynthesis pathway.Collectively,OsbZIP01 negatively regulates GA biosynthesis by restraining SD1 transcription,thereby affecting plant growth and development.

Paclobutrazol and Its Use in Fruit Production:A Review

There are documentary records referring to paclobutrazol(PBZ)as a growth bioregulator that inhibits the gibberellin synthesis and its application increases yields in fruit and vegetable crop productions.Its agronomic management includes it as an emerging technology to reduce vigour,promote flower induction and flower development in fruit trees with increased economic returns.Its use is banned in some countries because of concerns about residues that can cause harmful effects on the environment.Therefore,the aim of this article was to collect,analyse and summarise relevant information on the use of PBZ in fruit tree production and its possible risks to the environment.The results obtained indicated that the application of PBZ can be effective in solving some problems related to flowering if it is applied in the right amount and at the right time.However,it is necessary to elucidate the physiological processes with which it is associated and its response to be taken into account to increase yield.PBZ is currently used in fruit trees such as mango,lime,apple and guava,increasing their productivity.However,some studies have shown its residual effect on the environment.Therefore,PBZ is a viable strategy,because it presents a series of advantages in the production of fruit trees.However,it is vital to generate protocols that seek its regulation with a rational and sustainable approach.

Activation of gibberellin 2-oxidase 6 decreases active gibberellin levels and creates a dominant semi-dwarf phenotype in rice (Oryza sativa L.)

Gibberellin （GA） 2-oxidase plays a key role in the GA catabolic pathway through 2β-hydroxylation.In the present study,we isolated a CaMV 35S-enhancer activation tagged mutant,H032.This mutant exhibited a dominant dwarf and GA-deficient phenotype,with a final stature that was less than half of its wild-type counterpart.The endogenous bioactive GAs are markedly decreased in the H032 mutant,and application of bioactive GAs （GA3 or GA4） can reverse the dwarf phenotype.The integrated T-DNA was detected 12.8 kb upstream of the OsGA2ox6 in the H032 genome by TAIL-PCR.An increased level of OsGA2ox6 mRNA was detected at a high level in the H032 mutant,which might be due to the enhancer role of the CaMV 35S promoter.RNAi and ectopic expression analysis of OsGA2ox6 indicated that the dwarf trait and the decreased levels of bioactive GAs in the H032 mutant were a result of the up-regulation of the OsGA2ox6 gene.BLASTP analysis revealed that OsGA2ox6 belongs to the class III of GA 2-oxidases,which is a novel type of GA2ox that uses C20-GAs （GA12 and/or GA53） as the substrates.Interestingly,we found that a GA biosynthesis inhibitor,paclobutrazol,positively regulated the OsGA2ox6 gene.Unlike the over-expression of OsGA2ox1,which led to a high rate of seed abortion,the H032 mutant retained normal flowering and seed production.These results indicate that OsGA2ox6 mainly affects plant stature,and the dominant dwarf trait of the H032 mutant can be used as an efficient dwarf resource in rice breeding.