Genetics and evolution of leaf development

Compound leaves and flowers

 

The wild-type, pinnate pea leaf is a more complex structure than a simple leaf. It bears different organ types; stipules, leaflets and tendrils, that are initiated in sequence as the leaf develops. Flowers are also complex structures that initiate different organ types sequentially; sepals, petals, stamens and carpels (Figure 8).

 

 

 

Figure 8. Pea floral development.

Scanning electron micrograph of a pea floral meristem (left) with initiating sepal primordia (S), carpel (C), and common primordia (CP), which subsequently divide into petal (p) and stamen (s) primordia.Two fully expanded flowers on an inflorescence (right) with green sepals and pink petals visible.

 

Since LEAFY/UNIFOLIATA activates other transcription factors required for floral development, it seemed plausible that related transcription factors might be activated by UNIFOLIATA during pea leaf development. In collaboration with the University of Hobart, we found that a LEAFY co-regulator, known as UNUSUAL FLORAL ORGANS in Arabidopsis (Lee et al., 1996, Current Biology 7: 95-104) and STAMINA PISTILLOIDA in pea, has a role in flower and leaf development in pea (Taylor et al., 2001, Plant Cell 13; 31-46). However, APETALA1, which is activated by LEAFY during flower development in Arabidopsis (Parcy et al., 1998, Nature 395: 561-566) is not involved. The pea orthologue of APETALA1, known as PROLIFERATING INFLORESCENCE MERISTEM, is not expressed in leaves and the proliferating inflorescence meristem mutant produces normal, pinnate leaves (Hofer et al., 2002, Plant Physiology 129: 1150-1159).

 

We are currently investigating other floral transcription factors that may play a role in pea compound leaf architecture.

 

Papers from our lab are highlighted in yellow.

 

Norwich Research Park, Colney, Norwich NR4 7UH, UK