Patterning the female side of Arabidopsis: the importance of hormones

Abstract

The study of floral organ development has been a driving force in plant developmental biology research for the last two decades, and there is now an enormous wealth of information about the genetic networks underlying the specification of floral organ identity and the acquisition of its final morphology and function. These and parallel studies on leaf morphogenesis and development have made evident the common evolutionary origin of all plant lateral organs and the recurrent use of variations in the regulatory circuits involved in the shaping of leaves and flowers. This review summarizes the latest progress on the study of the development of the gynoecium, the female reproductive organ of the flower, stressing the connections with the developmental programme of leaf morphogenesis, and highlighting the common role of hormonal cues in these processes.

Hormones talking

“…29 The medial tissues, the region where cytokinin signaling was observed in developing gynoecia, are considered to have meristematic properties. [4][5][6]30 Are we observing in the cytokinin-treated young gynoecia, a similar process to what Yoshida et al propose to naturally occur in the shoot apical meristem? The external growth of the medial tissue could be explained by the cytokinin-inducible promotion of the meristematic activity of the medial tissue, which is then re-directed by auxin to produce a new ectopic "lateral organ."…”

“…This "hollow tube" elongates while two internal ridges (medial ridges) grow toward each other until they fuse and give rise to septum and placenta. [3][4][5][6][7] Different internal and external tissues of the gynoecium and later the fruit, such as the ovules, placenta, transmitting tract, septum and replum, style, and stigma also derive from the medial tissues. 4,5 Different factors guide the processes that exquisitely shape the gynoecium and fruit, and hormones are an important part of these factors.…”

Shedding light on flower development

“…2,[26][27][28][29] Meanwhile, numerous recent studies have investigated the relationship between phyB and phytohormones, with a large focus on auxin pathways. Indeed, phytochrome signaling has been shown to influence auxin pathways at different levels: auxin production, auxin distribution and sensitivity to auxin signals (reviewed in ref.…”

SEUSSandAINTEGUMENTAMediate Patterning and Ovule Initiation during Gynoecium Medial Domain Development

“…One speculation is that SEU and ANT mediate the action of an unidentified regulator of CRC expression that is differentially localized or active along the apical/basal axis of the gynoecium. Because a variety of experiments indicate that auxin signaling provides positional information along this axis (Sessions et al, 1997;Nemhauser et al, 2000;Balanza et al, 2006), it is possible that this proposed factor would be auxin dependent in some fashion.…”

“…Many mutations that affect the development of the medial ridge-derived structures have been identified Ferrandiz et al, 1999;Sessions, 1999;Alvarez and Smyth, 2002;Balanza et al, 2006). However, many of these genes share functional redundancy, and more severe alterations of medial ridge development have been reported in a variety of double mutants.…”