Many microbes enter a state of low metabolic activity, called quiescence, when the conditions for growth and division become unfavorable. The transition from active proliferation to quiescence involves a comprehensive restructuring of cellular metabolism, accumulation of storage compounds, and an orderly exit from the cell cycle. This kind of proliferation-to-quiescence switch has been extensively studied […]
The chloroplast is in constant communication with the nucleus via so-called retrograde signaling. This signaling, which can take many molecular forms, is important for maintaining chloroplast function. In this paper by Duan et al. we learn that interfering with plastid DNA replication, either through mutation of plastid-targeted replication factors, or by specific drugs, leads to […]
Chlamydomonas, like many green algae, divides by so-called “multiple fission” where the mother cell can grow many-fold in size before undergoing a series of rapid divisions. The dramatic separation of cell growth from cell division makes Chlamydomonas an attractive system to study genetic control of cell size homeostasis. In this paper by Cross, we learn […]
The contractile actomyosin ring (CAR) would be familiar to most students of cell biology. It is often assigned a major role in the formation of the cleavage furrow that bisects the cell during cytokinesis. The contractile force of the ring is generated by type-II myosin motor proteins pulling on actin filaments. However, although division by […]
When sea water freezes, it forms not a solid mass of ice, but rather a frozen matrix criss-crossed by tiny brine-filled channels. It is within these brine channels in the Antarctic sea ice that the psychrophilic (cold-loving) green alga ICE-L lives. How is it able to thrive in such a seemingly hostile environment of extreme […]
Carbon concentration mechanisms (CCMs) refer to a diverse set of strategies by which photosynthetic organisms increase the amount of carbon dioxide available to the carbon-fixing enzyme Rubisco. The cyanobacterial CCM relies on the carboxysome, a membraneless microcompartment with a core of densely packed Rubisco holoenzymes surrounded by a proteinaceous shell. Each holoenzyme is composed of […]
The thylakoid membranes inside the chloroplasts house the major protein complexes required for photosynthesis, including photosystems I and II (PSI/II), the b6f complex and ATP synthase. To optimize photosynthetic efficiency, the distribution and abundance of these complexes are dynamically regulated in response to varying light and growth conditions. However, to study how the spatial organization […]
In this paper, Moreno et al. investigate how nitrate affects the balance between cell proliferation and cell expansion in shoots during early seedling development. They note that the cells in Arabidopsis cotyledons undergo considerable enlargement, and that the increase in cell size is correlated with a switch from the mitotic cell cycle to endoreplication. During […]
Genome duplications are common in plants and thought to be an important contributor to evolutionary innovations, but the increase in ploidy that results from a genome duplication also presents challenges for reproduction. Because there are four sets of homologous chromosomes in the derived tetraploid (instead of two in the diploid ancestor), establishing one-to-one pairing between […]