The transcription factor PpRKD evokes female developmental fate in the sexual reproductive organs of Physcomitrium patens.

The sexual reproductive organs of bryophytes - in which gametes necessary for fertilization are produced, namely, male antheridia and female archegonia - are formed from vegetative haploid gametophytes. In dioicous bryophytes such as Marchantia polymorpha, the genes within the sex-determining regions in distinct sexual strains have been identified. However, in monoicous bryophytes such as Physcomitrium patens, how the two sex fates are specified on the same gametophyte remained unknown.

Sexual reproduction: Is the genetic pathway for female germ cell specification conserved in land plants?

Land plants share several core factors responsible for female gametophyte development, despite their differing structures and developmental programs. New work providing molecular dissection of reproductive phases in non-angiosperm plants is a powerful tool for elucidating the underlying genetic network.

Protocol: an improved method for inducing sporophyte generation in the model moss Physcomitrium patens under nitrogen starvation.

Background: Land plants exhibit a haplodiplontic life cycle, whereby multicellular bodies develop in both the haploid and diploid generations. The early-diverging land plants, known as bryophytes, have a haploid-dominant life cycle, in which a short-lived multicellular body in the diploid generation, known as the sporophyte, develops on the maternal haploid gametophyte tissues. The moss Physcomitrium (Physcomitrella) patens has become one of the most powerful model systems in evolutionary plant developmental studies.

CLE-HAR1 Systemic Signaling and NIN-Mediated Local Signaling Suppress the Increased Rhizobial Infection in the Mutant of .

Legumes survive in nitrogen-limited soil by forming a symbiosis with rhizobial bacteria. During root nodule symbiosis, legumes strictly control the development of their symbiotic organs, the nodules, in a process known as autoregulation of nodulation (AON). The study of hypernodulation mutants has elucidated the molecular basis of AON.

PLENTY, a hydroxyproline O-arabinosyltransferase, negatively regulates root nodule symbiosis in Lotus japonicus.

Legumes can survive in nitrogen-deficient environments by forming root-nodule symbioses with rhizobial bacteria; however, forming nodules consumes energy, and nodule numbers must thus be strictly controlled. Previous studies identified major negative regulators of nodulation in Lotus japonicus, including the small peptides CLAVATA3/ESR (CLE)-RELATED-ROOT SIGNAL1 (CLE-RS1), CLE-RS2, and CLE-RS3, and their putative major receptor HYPERNODULATION AND ABERRANT ROOT FORMATION1 (HAR1). CLE-RS2 is known to be expressed in rhizobia-inoculated roots, and is predicted to be post-translationally arabinosylated, a modification essential for its activity.

Leguminous plants: inventors of root nodules to accommodate symbiotic bacteria.

Legumes and a few other plant species can establish a symbiotic relationship with nitrogen-fixing rhizobia, which enables them to survive in a nitrogen-deficient environment. During the course of nodulation, infection with rhizobia induces the dedifferentiation of host cells to form primordia of a symbiotic organ, the nodule, which prepares plants to accommodate rhizobia in host cells. While these nodulation processes are known to be genetically controlled by both plants and rhizobia, recent advances in studies on two model legumes, Lotus japonicus and Medicago truncatula, have provided great insight into the underlying plant-side molecular mechanism.

Endoreduplication-mediated initiation of symbiotic organ development in Lotus japonicus.

Many leguminous plants have a unique ability to reset and alter the fate of differentiated root cortical cells to form new organs of nitrogen-fixing root nodules during legume-Rhizobium symbiosis. Recent genetic studies on the role of cytokinin signaling reveal that activation of cytokinin signaling is crucial to the nodule organogenesis process. However, the genetic mechanism underlying the initiation of nodule organogenesis is poorly understood due to the low number of genes that have been identified.

A Positive Regulator of Nodule Organogenesis, NODULE INCEPTION, Acts as a Negative Regulator of Rhizobial Infection in Lotus japonicus.

Legume-rhizobium symbiosis occurs in specialized root organs called nodules. To establish the symbiosis, two major genetically controlled events, rhizobial infection and organogenesis, must occur. For a successful symbiosis, it is essential that the two phenomena proceed simultaneously in different root tissues.