The peach (Prunus persica L. Batsch) genome harbours 10 KNOX genes, which are differentially expressed in stem development, and the class 1 KNOPE1 regulates elongation and lignification during primary growth

Abstract

The KNOTTED-like (KNOX) genes encode homeodomain transcription factors and regulate several processes of plant organ development. The peach (Prunus persica L. Batsch) genome was found to contain 10 KNOX members (KNOPE genes); six of them were experimentally located on the Prunus reference map and the class 1 KNOPE1 was found to link to a quantitative trait locus (QTL) for the internode length in the peach×Ferganensis population. All the KNOPE genes were differentially transcribed in the internodes of growing shoots; the KNOPE1 mRNA abundance decreased progressively from primary (elongation) to secondary growth (radial expansion). During primary growth, the KNOPE1 mRNA was localized in the cortex and in the procambium/metaphloem zones, whereas it was undetected in incipient phloem and xylem fibres. KNOPE1 overexpression in the Arabidopsis bp4 loss-of-function background (35S:KNOPE1/bp genotype) restored the rachis length, suggesting, together with the QTL association, a role for KNOPE1 in peach shoot elongation. Several lignin biosynthesis genes were up-regulated in the bp4 internodes but repressed in the 35S:KNOPE1/bp lines similarly to the wild type. Moreover, the lignin deposition pattern of the 35S:KNOPE1/bp and the wild-type internodes were the same. The KNOPE1 protein was found to recognize in vitro one of the typical KNOX DNA-binding sites that recurred in peach and Arabidopsis lignin genes. KNOPE1 expression was inversely correlated with that of lignin genes and lignin deposition along the peach shoot stems and was down-regulated in lignifying vascular tissues. These data strongly support that KNOPE1 prevents cell lignification by repressing lignin genes during peach stem primary growth.

Diverse functions of KNOX transcription factors in the diploid body plan of plants

“…The loss-of-function mutants fail to maintain shoot meristems [16][17][18]. In addition, class I KNOX genes are involved in distinct aspects of developmental processes, such as leaf dissection in compound leaf species, internode elongation, inflorescence architecture and establishment of vascular connections between parasitic plants and their hosts [19][20][21][22][23][24]. Thus, the class I KNOX gene regulatory module has been recruited to various developmental processes during the evolution of shoot systems.…”

Molecular Regulation of Storage Root Formation and Development in Sweet Potato

“…In Arabidopsis, a mutation in the second enzyme (C4H) of lignin biosynthesis pathway decreased levels of several different classes of phenylpropanoid end products and exhibited reduced lignin deposition, altered lignin monomer content, and a collapsed xylem phenotype (Schilmiller et al 2009). In this context of cross talk between establishment and development of the cambium meristem on the one hand and lignification on the other, it is interesting to note that a class I knotted-like gene (knope1) prevented cell lignification by repressing lignin genes during peach stem primary growth (Testone et al 2012), suggesting the role of knox genes in suppressing lignin biosynthesis during storage root formation in sweet potato.…”

Genome-wide analysis reveals phytohormone action during cassava storage root initiation

“…The expression pattern of CCOMT and CAD indicated that lignin biosynthesis was reduced during the early stage of SR development. In addition, upregulation of KNOX1 in I-stage and S-stage was negatively correlated with the expression of lignin biosynthesis key genes (CCOMT and CAD) (Guo et al 2001;Townsley et al 2013) suggesting that reduction of lignin biosynthesis corresponds to SR development (Firon et al 2013;Testone et al 2012).…”