Knechtle Philipp, Kaufmann Andreas, Cavicchioli Daniele, Philippsen Peter
Molecular Microbiology, Biozentrum der Universität Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland.
Fungal Genet Biol. 2008 Jun;45(6):829-38. doi: 10.1016/j.fgb.2008.03.010. Epub 2008 Mar 25.
The development from young, slowly growing hyphae to fast growing hyphae in filamentous fungi is referred to as hyphal maturation. We have identified the Paxillin-like protein AgPxl1 in Ashbyagossypii as a developmental protein that is specifically required for hyphal maturation. The early development of A.gossypii strains lacking AgPxl1 is indistinguishable from wild-type. However, at later developmental stages the maximal hyphal extension rate is less than half compared to wild-type and apical branching is affected. Apical branching is characterised as the symmetric division of fast growing hyphal tips resulting in two sister hyphae. In Agpxl1Delta strains two thirds of the apical branching events lead to asymmetric sister hyphae where growth of one branch is either completely aborted or slowed down while extension of the other branch is not affected. This suggests that AgPxl1 plays a role in the organisation of growth and efficient division of growth upon apical branching in mature mycelia. The conserved C-terminal LIM domains are necessary for AgPxl1 function and also contribute to tip localisation. AgCLA4, a PAK-like kinase, is epistatic to AgPXL1 and robust localisation of AgPxl1 depends on AgCla4. This suggests that AgCla4 acts upstream of AgPxl1.
丝状真菌中从年轻、生长缓慢的菌丝向快速生长的菌丝的发育过程被称为菌丝成熟。我们在棉阿舒囊霉中鉴定出类桩蛋白AgPxl1是一种发育蛋白，它是菌丝成熟所特需的。缺乏AgPxl1的棉阿舒囊霉菌株的早期发育与野生型没有区别。然而，在发育后期，其最大菌丝延伸率不到野生型的一半，且顶端分支受到影响。顶端分支的特征是快速生长的菌丝顶端进行对称分裂，产生两个姐妹菌丝。在Agpxl1Delta菌株中，三分之二的顶端分支事件导致不对称的姐妹菌丝，其中一个分支的生长要么完全停止，要么减缓，而另一个分支的延伸不受影响。这表明AgPxl1在成熟菌丝体顶端分支时的生长组织和高效生长分裂中发挥作用。保守的C末端LIM结构域对AgPxl1的功能是必需的，并且也有助于其顶端定位。AgCLA4是一种类PAK激酶，对AgPXL1上位，且AgPxl1的稳定定位依赖于AgCla4。这表明AgCla4在AgPxl1的上游起作用。
