Sensor histidine kinases mediate ABA and osmostress signaling in the moss Physcomitrium patens.

To survive fluctuating water availability on land, terrestrial plants must be able to sense water stresses, such as drought and flooding. The plant hormone abscisic acid (ABA) and plant-specific SNF1-related protein kinase 2 (SnRK2) play key roles in plant osmostress responses. We recently reported that, in the moss Physcomitrium patens, ABA and osmostress-dependent SnRK2 activation requires phosphorylation by an upstream RAF-like kinase (ARK).

An Ancestral Role for CONSTITUTIVE TRIPLE RESPONSE1 Proteins in Both Ethylene and Abscisic Acid Signaling.

Land plants have evolved adaptive regulatory mechanisms enabling the survival of environmental stresses associated with terrestrial life. Here, we focus on the evolution of the regulatory CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) component of the ethylene signaling pathway that modulates stress-related changes in plant growth and development. First, we compare CTR1-like proteins from a bryophyte, Physcomitrella patens (representative of early divergent land plants), with those of more recently diverged lycophyte and angiosperm species (including Arabidopsis [Arabidopsis thaliana]) and identify a monophyletic CTR1 family.

Studies of Physcomitrella patens reveal that ethylene-mediated submergence responses arose relatively early in land-plant evolution.

Colonization of the land by multicellular green plants was a fundamental step in the evolution of life on earth. Land plants evolved from fresh-water aquatic algae, and the transition to a terrestrial environment required the acquisition of developmental plasticity appropriate to the conditions of water availability, ranging from drought to flood. Here we show that extant bryophytes exhibit submergence-induced developmental plasticity, suggesting that submergence responses evolved relatively early in the evolution of land plants.

The angiosperm gibberellin-GID1-DELLA growth regulatory mechanism: how an "inhibitor of an inhibitor" enables flexible response to fluctuating environments.

The phytohormone gibberellin (GA) has long been known to regulate the growth, development, and life cycle progression of flowering plants. However, the molecular GA-GID1-DELLA mechanism that enables plants to respond to GA has only recently been discovered. In addition, studies published in the last few years have highlighted previously unsuspected roles for the GA-GID1-DELLA mechanism in regulating growth response to environmental variables.

Specialization of the Golden2-like regulatory pathway during land plant evolution.

* The development of photosynthetic competence is a key requirement for all land plants and many aquatic algae. Previous work has demonstrated that a pair of Golden2-like (GLK) transcription factors regulates chloroplast development in diverse land plants, in that recessive glk1;glk2 mutants are pale green and fail to accumulate components of the light-harvesting machinery. To determine the extent to which the GLK pathway has diverged in land plants, we compared GLK gene function in the flowering plant Arabidopsis thaliana and the moss Physcomitrella patens.

Step-by-step acquisition of the gibberellin-DELLA growth-regulatory mechanism during land-plant evolution.

Angiosperms (flowering plants) evolved relatively recently and are substantially diverged from early land plants (bryophytes, lycophytes, and others [1]). The phytohormone gibberellin (GA) adaptively regulates angiosperm growth via the GA-DELLA signaling mechanism [2-7]. GA binds to GA receptors (GID1s), thus stimulating interactions between GID1s and the growth-repressing DELLAs [8-12].

A conserved transcription factor mediates nuclear control of organelle biogenesis in anciently diverged land plants.

Land plant chloroplasts evolved from those found in the green algae. During land plant evolution, nuclear regulatory mechanisms have been modified to produce morphologically and functionally diverse chloroplasts in distinct developmental contexts. At least some of these mechanisms evolved independently in different plant lineages.