Weeds of change: Cardamine hirsuta as a new model system for studying dissected leaf development

• Published in: Journal of plant research Vol. 123; no. 1; pp. 25 - 33
• Main Authors: Canales, Claudia, Barkoulas, Michalis, Galinha, Carla, Tsiantis, Miltos
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01-01-2010; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Botany; Cardamine - anatomy & histology; Cardamine - growth & development; Cell division; Gene expression; Genes, Homeobox - physiology; Genes, Plant; Homeodomain Proteins - genetics; Homeodomain Proteins - physiology; Insulator Elements - physiology; JPR Symposium; Leaves; Life Sciences; Meristem - anatomy & histology; Meristem - growth & development; Plant Biochemistry; Plant Ecology; Plant Growth Regulators - physiology; Plant Leaves - anatomy & histology; Plant Leaves - growth & development; Plant Physiology; Plant Sciences; Proteins; KNOX proteins; Leaf development; Auxin
• ISSN: 0918-9440; 1618-0860
• DOI: 10.1007/s10265-009-0263-3

Cardamine hirsuta
, a small crucifer closely related to the model organism
Arabidopsis thaliana
, offers high genetic tractability and has emerged as a powerful system for studying the genetic basis for diversification of plant form. Contrary to
A. thaliana
, which has simple leaves,
C. hirsuta
produces dissected leaves divided into individual units called leaflets. Leaflet formation requires activity of Class I KNOTTED1-like homeodomain (KNOX) proteins, which also promote function of the shoot apical meristem (SAM). In
C. hirsuta
,
KNOX
genes are expressed in the leaves whereas in
A. thaliana
their expression is confined to the SAM, and differences in expression arise through cis-regulatory divergence of KNOX regulation. KNOX activity in
C. hirsuta
leaves delays the transition from proliferative growth to differentiation thus facilitating the generation of lateral growth axes that give rise to leaflets. These axes reflect the sequential generation of cell division foci across the leaf proximodistal axis in response to auxin activity maxima, which are generated by the PINFORMED1 (PIN1) auxin efflux carriers in a process that resembles organogenesis at the SAM. Delimitation of
C. hirsuta
leaflets also requires the activity of
CUP
SHAPED
COTYLEDON
(
CUC
) genes, which direct formation of organ boundaries at the SAM. These observations show how species-specific deployment of fundamental shoot development networks may have sculpted simple versus dissected leaf forms. These studies also illustrate how extending developmental genetic studies to morphologically divergent relatives of model organisms can greatly help elucidate the mechanisms underlying the evolution of form.