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

Abstract

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 OsIDD2, 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 OsIDD2-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 OsIDD2 negatively regulates the transcription of genes involved in lignin biosynthesis, cinnamyl alcohol dehydrogenase 2 and 3 (CAD2 and 3), and sucrose metabolism, sucrose synthase 5 (SUS5), whereas an AlphaScreen assay, which can detect the interaction between TFs and their target DNA sequences, directly confirmed the interaction between OsIDD2 and the target sequences located in the promoter regions of CAD2 and CAD3. Based on these observations, we conclude that OsIDD2 is negatively involved in SCW formation and other biological events by downregulating its target genes.

Full-Length Transcriptome Survey and Expression Analysis of Cassia obtusifolia to Discover Putative Genes Related to Aurantio-Obtusin Biosynthesis, Seed Formation and Development, and Stress Response

“…Zinc finger TFs possessed the zinc finger motif and played an extensive role in seed germination, secondary wall formation, and response to heat stress. MYB TFs were involved in controlling various processes like responses to biotic and abiotic stresses, development, differentiation, secondary metabolism, and defense [ 50 , 52 , 53 ]. In plants, the Auxin response factor (ARF) transcription factor family regulates gene expression in response to auxin and plays essential part in the root and gametophyte [ 54 , 55 ].…”

Current Models for Transcriptional Regulation of Secondary Cell Wall Biosynthesis in Grasses

“…Besides the NAC, MYB and TALE families, the C2H2 family is listed in TF families that have the most abundant members co-expressed with secondary cell wall structural genes in rice and Arabidopsis ( Hirano et al, 2013a ). One C2H2 member named OsIDD2 was proven to be a negative regulator of secondary wall formation ( Huang et al, 2017 ). Overexpressing OsIDD2 in rice decreases the lignin content with a reduced expression of several structural genes involved in lignin, cellulose, and sucrose biosynthesis.…”

Grass secondary cell walls, Brachypodium distachyon as a model for discovery

“…Arabidopsis thaliana C3H14 is a direct activator of lignin, cellulose and hemicellulose biosynthesis genes and may be a repressor of MYB cell wall activators (Ko et al, 2009;Kim et al, 2012). Conversely, the INDETERMINATE family C2H2-type zincfinger transcription factor in rice, OsIDD2, interacts with the ID motif to repress the expression of lignin-associated genes (Huang et al, 2018). Analysis of mutants and transgenic plants suggests that OsIDD2 directly represses lignin-associated gene expression and indirectly secondary wall CESA genes.…”