Hurtado C A, Beckerich J M, Gaillardin C, Rachubinski R A
Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
J Bacteriol. 2000 May;182(9):2376-86. doi: 10.1128/JB.182.9.2376-2386.2000.
Dimorphism in fungi is believed to constitute a mechanism of response to adverse conditions and represents an important attribute for the development of virulence by a number of pathogenic fungal species. We have isolated YlRAC1, a gene encoding a 192-amino-acid protein that is essential for hyphal growth in the dimorphic yeast Yarrowia lipolytica and which represents the first Rac homolog described for fungi. YlRAC1 is not an essential gene, and its deletion does not affect the ability to mate or impair actin polarization in Y. lipolytica. However, strains lacking functional YlRAC1 show alterations in cell morphology, suggesting that the function of YlRAC1 may be related to some aspect of the polarization of cell growth. Northern blot analysis showed that transcription of YlRAC1 increases steadily during the yeast-to-hypha transition, while Southern blot analysis of genomic DNA suggested the presence of several RAC family members in Y. lipolytica. Interestingly, strains lacking functional YlRAC1 are still able to grow as the pseudohyphal form and to invade agar, thus pointing to a function for YlRAC1 downstream of MHY1, a previously isolated gene encoding a C(2)H(2)-type zinc finger protein with the ability to bind putative stress response elements and whose activity is essential for both hyphal and pseudohyphal growth in Y. lipolytica.
真菌中的二态性被认为是一种应对不利条件的机制，并且是许多致病真菌物种毒力发展的一个重要属性。我们分离出了YlRAC1，这是一个编码192个氨基酸蛋白质的基因，对于二态酵母解脂耶氏酵母的菌丝生长至关重要，并且它代表了首次描述的真菌Rac同源物。YlRAC1不是必需基因，其缺失并不影响解脂耶氏酵母的交配能力或肌动蛋白极化。然而，缺乏功能性YlRAC1的菌株在细胞形态上出现改变，这表明YlRAC1的功能可能与细胞生长极化的某些方面有关。Northern印迹分析表明，在酵母到菌丝的转变过程中，YlRAC1的转录稳步增加，而基因组DNA的Southern印迹分析表明解脂耶氏酵母中存在几个RAC家族成员。有趣的是，缺乏功能性YlRAC1的菌株仍然能够以假菌丝形式生长并侵入琼脂，因此表明YlRAC1在MHY1下游起作用，MHY1是先前分离的一个基因，编码一种具有结合假定应激反应元件能力的C(2)H(2)型锌指蛋白，其活性对于解脂耶氏酵母的菌丝和假菌丝生长都至关重要。
