Evaluation of reference genes and characterization of the MYBs in xylem radial change of Chinese fir stem

Abstract

The radial change (RC) of tree stem is the process of heartwood formation involved in complex molecular mechanism. Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), an evergreen species, is an important fast-growing timber tree in southern China. In this study, the top four stable genes (IDH, UBC2, RCA and H2B) were selected in RC tissues of 15 years old Chinese fir stem (RC15) and the genes (H2B, 18S, TIP41 and GAPDH) were selected in RC tissues of 30 years old Chinese fir stem (RC30). The stability of the reference genes is higher in RC30 than in RC15. Sixty-one MYB transcripts were obtained on the PacBio Sequel platform from woody tissues of one 30 years old Chinese fir stem. Based on the number of MYB DNA-binding domain and phylogenetic relationships, the ClMYB transcripts contained 21 transcripts of MYB-related proteins (1R-MYB), 39 transcripts of R2R3-MYB proteins (2R-MYB), one transcript of R1R2R3-MYB protein (3R-MYB) belonged to 18 function-annotated clades and two function-unknown clades. In RC woody tissues of 30 years old Chinese fir stem, ClMYB22 was the transcript with the greatest fold change detected by both RNA-seq and qRT-PCR. Reference genes selected in this study will be helpful for further verification of transcript abundance patterns during the heartwood formation of Chinese fir.

The Regulation of Xylem Development by Transcription Factors and Their Upstream MicroRNAs

“…The MYB family, as one of the largest transcription factor families in plants, was initially found to be involved in the stress response of plants and was later found to play an important role in the regulation of xylem development [ 32 , 33 ]. MYB transcription factors mainly participate in regulating the secondary cell wall formation during xylem differentiation, constituting a complex regulatory network with MYB46 and MYB83 as the main switches ( Figure 2 ).…”