Novel phytohormones involved in long-range signaling.

Communication between distant organs is an essential feature of multicellular organisms. Plants are no exception to this rule and long-range signals are involved in the regulation of many aspects of organ growth and development. In this review, we use two specific examples to illustrate this point.

BRX mediates feedback between brassinosteroid levels and auxin signalling in root growth.

Brassinosteroid and auxin decisively influence plant development, and overlapping transcriptional responses to these phytohormones suggest an interaction between the two pathways. However, whether this reflects direct feedback or merely parallel inputs on common targets is unclear. Here we show that in Arabidopsis roots, this interaction is mediated by BREVIS RADIX (BRX), which is required for optimal root growth.

Characterization of the plant-specific BREVIS RADIX gene family reveals limited genetic redundancy despite high sequence conservation.

To date, the function of most genes in the Arabidopsis (Arabidopsis thaliana) genome is unknown. Here we present the first analysis of the novel, plant-specific BRX (BREVIS RADIX) gene family. BRX has been identified as a modulator of root growth through a naturally occurring loss-of-function allele.

The Arabidopsis transcription factor HY5 integrates light and hormone signaling pathways.

The role of the Arabidopsis transcription factor LONG HYPOCOTYL 5 (HY5) in promoting photomorphogenic development has been extensively characterized. Although the current model for HY5 action largely explains its role in this process, it does not adequately address the root phenotype observed in hy5 mutants. In our search for common mechanisms underlying all hy5 traits, we found that they are partly the result of an altered balance of signaling through the plant hormones auxin and cytokinin.

Natural genetic variation in Arabidopsis identifies BREVIS RADIX, a novel regulator of cell proliferation and elongation in the root.

Mutant analysis has been tremendously successful in deciphering the genetics of plant development. However, less is known about the molecular basis of morphological variation within species, which is caused by naturally occurring alleles. In this study, we succeeded in isolating a novel regulator of root growth by exploiting natural genetic variation in the model plant Arabidopsis.