Origin of a Subgenome and Genome Evolution of Allotetraploid Cotton Species

Cotton(Gossypium spp.)is one of the most important economic crops in the world and also a major source of natural fiber,oil,and protein.The morphology of cotton species varies from trailing herbaceous perennials to trees<10 m.Like other important crops,modern cotton cultivars are polyploids and have gone through polyploidization,evolution,and domestication.The cotton genus comprises approximately 45 diploid(2n=2x=26)and seven tetraploid species(2n=4x=52)(Guan et al.,2014).

Osmotic Stress Modulates the Balance between Exocytosis and Clathrin-Mediated Endocytosis in Arabidopsis thaliana

The sessile life style of plants creates the need to deal with an often adverse environment, in which water availability can change on a daily basis, challenging the cellular physiology and integrity. Changes in os- motic conditions disrupt the equilibrium of the plasma membrane： hypoosmotic conditions increase and hyperosmotic environment decrease the cell volume. Here, we show that short-term extracellular osmotic treatments are closely followed by a shift in the balance between endocytosis and exocytosis in root mer- istem cells. Acute hyperosmotic treatments （ionic and nonionic） enhance clathrin-mediated endocytosis simultaneously attenuating exocytosis, whereas hypoosmotic treatments have the opposite effects. In addition to clathrin recruitment to the plasma membrane, components of early endocytic trafficking are essential during hyperosmotic stress responses. Consequently, growth of seedlings defective in elements of clathrin or early endocytic machinery is more sensitive to hyperosmotic treatments. We also found that the endocytotic response to a change of osmotic status in the environment is dominant over the presum- ably evolutionary more recent regulatory effect of plant hormones, such as auxin. These results imply that osmotic perturbation influences the balance between endocytosis and exocytosis acting through clathrin- mediated endocytosis. We propose that tension on the plasma membrane determines the addition or removal of membranes at the cell surface, thus preserving cell integrity.

ABP1： Finally Docking

Auxin, one of the plant hormones, is a key regulator of plant growth and development. At the cellular level, it controls different processes, such as cell expansion, division, and differentiation that are reflected by its regulatory role in a plethora of developmental mechanisms. An important feature of the auxin action is its differential distribution within tissues mediated by the polar auxin transport machinery, which can be dynamically regulated in response to internal and external stimuli. Receptors at the cell surface or cell interior are needed to sense and interpret fluctuations in the auxin distribution.