A zinc finger protein, interacted with cyclophilin,affects root development via IAA pathway in rice

The plant hormone auxin plays a crucial role in lateral root development. To better understand the rnolecular mechanisms underlying lateral root formation, an auxin-responsive gene OsCYP2 （Oso2g0121300） was characterized from rice. Compared to the wild type, OsCYP2-RNAi （RNA interference） lines exhibited distinctive defects in lateral root development. Yeast two-hybrid and glutathione S-transferase puIl-down results confirmed that OsCYP2 interacted with a C2HC-type zinc finger protein （OsZFP, O501g0252900） which is located in the rice nucleus. T2OsZFP-RNAi lines had significantly fewer lateral roots than did wild-type plants, which suggests a role for OsCYP2 and OsZFP in regulating lateral root development.Quantitative real-time polymerase chain reaction showed that the expression of certain Aux/IAA （auxin/indole-3- acetic acid） genes was altered in OsCYP2- and OsZFP-RNAi lines in response to IAA. These findings imply that OsCYP2 and OsZFP participate in IAA signal pathways controlling lateral root development. More importantly, OslAA11 showed functional redundancy not only in OsCYP2-RNAi lines but also in OsZFP-RNAi lines, which provides important clues for the elucidation of mechanisms controlling lateral root development in response to auxin.

OsIDD2, a zinc finger and INDETERMINATE DOMAIN protein, regulates secondary cell wall formation

Previously, we found 123 transcription factors（TFs） as candidate regulators of secondary cell wall（SCW）formation in rice by using phylogenetic and co-expression network analyses. Among them, we examined in this work the role of OsIDD_2, a zinc finger and indeterminate domain（IDD） family TF. Its overexpressors showed dwarfism, fragile leaves, and decreased lignin content, which are typical phenotypes of plants defective in SCW formation, whereas its knockout plants showed slightly increased lignin content.The RNA-seq and quantitative reverse transcription polymerase chain reaction analyses confirmed that some lignin biosynthetic genes were downregulated in the OsIDD_2-overexpressing plants, and revealed the same case for other genes involved in cellulose synthesis and sucrose metabolism. The transient expression assay using rice protoplasts revealed that OsIDD_2 negatively regulates the transcription of genes involved in lignin biosynthesis, cinnamyl alcohol dehydrogenase 2 and 3（CAD_2 and 3）, and sucrose metabolism, sucrose synthase 5（SUS_5）, whereas an Alpha Screen assay, which can detect the interaction between TFs and their target DNA sequences, directly confirmed the interaction between OsIDD_2 and the target sequences located in the promoter regions of CAD_2 and CAD_3. Based on these observations, we conclude that OsIDD_2 is negatively involved in SCW formation and other biological events by downregulating its target genes.