Actin organization and regulation during pollen tube growth

Pollen is the male gametophyte of seed plants and its tube growth is essential for successful fertilization.Mounting evidence has demonstrated that actin organization and regulation plays a central role in the process of its germination and polarized growth.The native structures and dynamics of actin are subtly modulated by many factors among which numerous actin binding proteins(ABPs)are the most direct and significant regulators.Upstream signals such as Ca^(2+),PIP_(2)(phosphatidylinositol-4,5-bis-phosphate)and GTPases can also indirectly act on actin organization through several ABPs.Under such elaborate regulation,actin structures show dynamically continuous modulation to adapt to the in vivo biologic functions to mediate secretory vesicle transportation and fusion,which lead to normal growth of the pollen tube.Many encouraging progress has been made in the connection between actin regulation and pollen tube growth in recent years.In this review,we summarize different factors that affect actin organization in pollen tube growth and highlight relative research progress.