Repression ofAS2by WOX family transcription factors is required for leaf development in Medicago and Arabidopsis

Abstract

WOX transcription factors are key regulators of meristematic activity in plants. The Medicago WOX gene, STF, functions in maintenance of leaf marginal meristem, analogous to the function of WUS in the shoot apical meristem. Both STF and WUS directly repress AS2 expression in their respective domains. Ectopic expression of AS2 with WUS promoter leads to a narrow leaf phenotype and other phenotypes similar to the wus mutant. We also found that a wox1 prs wus triple mutant produces much narrower leaf blades than the wox1 prs double mutant, indicating that WUS genetically interacts with WOX1 and PRS in Arabidopsis leaf blade development. Our data points to a general requirement for AS2 repression in meristematic regions to allow cell proliferation.The organogenesis of multicellular organisms needs the coordination of cell proliferation, differentiation and expansion.

Coordination of Leaf Development Across Developmental Axes

“…Given the adaxial–abaxial patterning defects in wox1 prs mutants, WOX1 and PRS are likely involved in feedback regulation of adaxial–abaxial patterning factors at later stages of development. Among the adaxial patterning factors, WOX1/PRS promote the expression of HD-ZIPIII genes in the developing leaf margins, likely in part through inhibition of miR165/166 (Figure 3A) [84] WOX1/PRS also repress the expression of AS2 , restricting its expression to the adaxial domain of the leaf margin [87,88]. Meanwhile, WOX1/PRS influence the expression of abaxial-specific genes as well.…”

HEADLESS, aWUSCHELhomolog, uncovers novel aspects of shoot meristem regulation and leaf blade development inMedicago truncatula

“…It is even likely that WUS has a redundant function in leaf blade development with other WOX genes. The wox1 prs wus triple mutant exhibits a noticeably narrower leaf blade compared with the wox1 prs double mutant, implicating that WUS might function in regulating leaf lateral blade outgrowth in Arabidopsis (Zhang and Tadege, 2015), although this has not been investigated in detail. However, in M. truncatula , the mutation of HDL results in clearly altered leaf shape, changing from a more or less oval shape in R108 to heart-shaped blades in the mutant, suggesting that HDL may regulate leaf development in the proximal–distal axis in contrast to the role of STF in regulating blade outgrowth in the medial–lateral axis.…”

Auxin polar transport flanking incipient primordium initiates leaf adaxial‐abaxial polarity patterning

“…It was reported recently that leaf polarity genes are regulated by auxin in the primordium (Caggiano et al ). The WOX genes are also known to regulate the expression of both adaxially and abaxially expressed transcription factors and miRNAs (Nakata et al ; Zhang et al ; Zhang and Tadege ). Several WOX genes carry auxin responsive elements (Figure ), and a recent report showed that several auxin responsive factors directly regulate the WOX genes (Guan et al ).…”