CLAUSA restricts tomato leaf morphogenesis and GOBLET expression

Abstract

SUMMARYLeaf morphogenesis and differentiation are highly flexible processes. The development of compound leaves is characterized by an extended morphogenesis stage compared with that of simple leaves. The tomato mutant clausa (clau) possesses extremely elaborate compound leaves. Here we show that this elaboration is generated by further extension of the morphogenetic window, partly via the activity of ectopic meristems present on clau leaves. Further, we propose that CLAU might negatively affect expression of the NAM/CUC gene GOBLET (GOB), an important modulator of compound-leaf development, as GOB expression is elevated in clau mutants and reducing GOB expression suppresses the clau phenotype. Expression of GOB is also elevated in the compound leaf mutant lyrate (lyr), and the remarkable enhancement of the clau phenotype by lyr suggests that clau and lyr affect leaf development and GOB in different pathways.

CLAUSA is a MYB Transcription Factor that Promotes Leaf Differentiation by Attenuating Cytokinin Signaling

“…Some aspects of the leaf phenotype caused by IPT7 overexpression are reminiscent of the clau phenotype, including a highly compound leaf, many ectopic meristems on the leaf, and an extension of the developmental window of leaflet morphogenesis (Bar et al, 2015). The simplified leaf phenotypes resulting from overexpression of CLAU and CKX were also similar.…”

“…We previously quantified the clau phenotype, demonstrating that clau leaves are on average 11 times more compound than wild-type leaves (Bar et al, 2015). The clau mutant phenotypes suggest that CLAU plays a central role in modulating the flexibility of leaf morphogenesis.…”

“…This extended morphogenesis is enabled by the activity of a meristematic region at the leaf margin, termed marginal blastozone (Hagemann and Gleissberg, 1996). The morphogenetic stage is particularly long in tomato, resulting in a wide diversity of leaf forms and unique developmental flexibility (Bar and Ori, 2014;Bar et al, 2015;. Recent studies have uncovered an even higher potential for prolonged morphogenesis in tomato leaf development, which is normally restricted by differentiation-promoting factors (Bar et al, 2015;Shani et al, 2010;Yanai et al, 2011).…”

“…The morphogenetic stage is particularly long in tomato, resulting in a wide diversity of leaf forms and unique developmental flexibility (Bar and Ori, 2014;Bar et al, 2015;. Recent studies have uncovered an even higher potential for prolonged morphogenesis in tomato leaf development, which is normally restricted by differentiation-promoting factors (Bar et al, 2015;Shani et al, 2010;Yanai et al, 2011). Characterization of mutants with extended or restricted morphogenesis has pointed to this potential and led to the identification of factors that balance morphogenesis and differentiation during leaf development (Sluis and Hake, 2015;Canales et al, 2010;Efroni et al, 2010;Bar and Ori, 2014;Blein et al, 2010).…”

“…CLAU is a potential negative regulator of KNOXI genes and of the boundary gene GOBLET (GOB) (Bar et al, 2015;Avivi et al, 2000;Jasinski et al, 2007Jasinski et al, , 2008Naz et al, 2013).…”