Homologies in Leaf Form Inferred from KNOXI Gene Expression During Development

  title={Homologies in Leaf Form Inferred from KNOXI Gene Expression During Development},
  author={Geeta Bharathan and Thomas E. Goliber and Christopher Moore and Sharon A. Kessler and Thinh Phu Pham and Neelima R. Sinha},
  pages={1858 - 1860}
KNOTTEDI-like homeobox (KNOXI) genes regulate development of the leaf from the shoot apical meristem (SAM) and may regulate leaf form. We examined KNOXI expression in SAMs of various vascular plants and found that KNOXI expression correlated with complex leaf primordia. However, complex primordia may mature into simple leaves. Therefore, not all simple leaves develop similarly, and final leaf morphology may not be an adequate predictor of homology. 

Coordination of leaf development via regulation of KNOX1 genes

Another aspect of KNOX1 regulation via a protein–protein interaction network involved in the natural variation in leaf shape could be utilized for fine-tuning leaf morphology during evolution without affecting the essential function of K NOX genes in the shoot.

The role of knox genes in plant development.

In plants with simple leaves, knox genes are expressed exclusively in the meristem and stem, but in dissected leaves, they are also expressed in leaf primordia, suggesting that they may play a role in the diversity of leaf form.

KNOX genes: versatile regulators of plant development and diversity

How KNOX proteins influence plant growth and development in a versatile context-dependent manner is discussed.

Evolution of leaf developmental mechanisms.

Evolution of leaf form is discussed in the context of the current understanding of leaf development, as this has emerged from molecular genetic studies in model organisms.

Role of Knox Genes in Shoot Development of Welwitschia mirabilis

The results show that W. mirabilis produces three pairs of leaflike organs with very distinct terminal fates, that the SAM is present and active even after these leaf pairs are initiated, and that the KNOX I class of genes are a good marker for meristem identity and maintenance.

Regulation of SHOOT MERISTEMLESS genes via an upstream-conserved noncoding sequence coordinates leaf development

Two evolutionarily conserved noncoding sequences within the 5′ upstream region of STM genes in both simple and compound leafed species across monocots and dicots are identified, revealing a regulatory point of leaf development mediated through a conserved, nonc coding sequence in STM gene expression.

Gene expression patterns in seed plant shoot meristems and leaves: homoplasy or homology?

It is argued here that the similarities may be homologous due to descent from ancestral roles in an ancestral shoot system, and the marginal blastozone that characterizes many angiosperm leaves appears to function in a manner mechanistically similar to the SAM.

Behavior of Leaf Meristems and Their Modification

Recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana are reviewed to understand how the gene Regulatory networks modulate leafMeristems to yield a substantial diversity of leaf forms during the course of evolution.

A developmental framework for dissected leaf formation in the Arabidopsis relative Cardamine hirsuta

It is shown that lateral leaflet formation in C. hirsuta requires the establishment of growth foci that form after leaf initiation, and evidence is provided that differential deployment of a fundamental mechanism polarizing cellular growth contributed to the diversification of leaf form during evolution.



KNAT1 induces lobed leaves with ectopic meristems when overexpressed in Arabidopsis.

It is shown that ectopic expression of KNAT1 in Arabidopsis transforms simple leaves into lobed leaves, and further suggest that kn1-related genes may have played a role in the evolution of leaf diversity.

A gene fusion at a homeobox locus: alterations in leaf shape and implications for morphological evolution.

This work describes here an instance of a spontaneously arisen fusion between a gene encoding a metabolic enzyme and a homeodomain protein, and suggests that such phenomena may have played a role in the evolution of form.

Overexpression of a homeobox gene, LeT6, reveals indeterminate features in the tomato compound leaf

The expression patterns of LeT 6 argue in favor of a fundamental role for LeT6 in morphogenesis of leaves in tomato and also suggest that variability in homeobox gene expression may account for some of the diversity in leaf form seen in nature.

Pea Compound Leaf Architecture Is Regulated by Interactions among the Genes UNIFOLIATA, COCHLEATA, AFILA, and TENDRIL-LESS

It is shown that UNI is expressed in the leaf blastozone over the period in which organ primordia are initiated and is downregulated at the time of leaf primordium determination, and proposed that the control of UNI expression by AF, TL, and COCH is important in the regulation of Blastozone activity and pattern formation in the compound leafPrimordium of the pea.

Overexpression of the maize homeo box gene, KNOTTED-1, causes a switch from determinate to indeterminate cell fates.

It is proposed that the KN1 homeo box gene plays a role in determining cell fate in maize and tobacco, and the consequences of KN1 overexpression appear to depend on the concentration ofKN1 and the timing of its expression during organogenesis.

Auxin effects on vascular differentiation in Ostrich fern

Surgical experiments have confirmed the capacity of a fern shoot apex to give rise to a mature vascular system in the absence of leaves. When the shoot apex of Matteuccia struthiopteris Tod. was

A knotted1-like homeobox gene in Arabidopsis is expressed in the vegetative meristem and dramatically alters leaf morphology when overexpressed in transgenic plants.

The hypothesis that class 1 kn1-like genes play a role in morphogenesis is supported by the characterization of two genes, KNAT1 and KNAT2 that were cloned from Arabidopsis using the kn1 homeobox as a heterologous probe.

The developmental gene Knotted-1 is a member of a maize homeobox gene family

It is shown that the Kn1 gene encodes a homeodomain-containing protein, the first identified in the plant kingdom, and may permit the isolation of genes that, like animal and fungal counter-parts, regulate cell fate determination.