1. Microtubule number and length determine cellular shape and function in Plasmodium
Quantitative analysis of salivary gland sporozoite lengths from the different lines. n indicates numbers of investigated sporozoites. Box plots represent 50% (boxes) and 95% (bars) of data with horizontal bar showing the median. *** and **** indicate P < 0.001 and P < 0.0001, respectively; ns: not significant; Kruskal–Wallis test; scale bar: 1 μm. Quantification of SiR‐tubulin fluorescence from 69 to 127 salivary gland‐derived sporozoites. Note the decrease in the fluorescence intensity of sporozoites expressing α1‐tubulin without introns as well as the decreased intensity and length of the chimeras. Linear correlation of sporozoite length and microtubule length reveals a R2 = 0.94. *, ** and **** indicate P < 0.05, P < 0.01 and P < 0.0001, respectively; ns: not significant; Kruskal–Wallis test. Shorter sporozoites exhibit higher curvatures and hence tighter circular motility on glass. Scale bar: 20 μm. Box plots represent 50% (boxes) and 95% (bars) of data with horizontal bar showing the median. * and **** indicate P < 0.05 and P < 0.0001, respectively; ns: not significant; Kruskal–Wallis test. Sporozoites with fewest microtubules (α2+++) show a motility defect. n indicates numbers of investigated sporozoites; numbers on grey bars indicate percentage of partially and persistently moving sporozoites. Sporozoites from lines with fewer microtubules move more frequently in apparent clockwise (CW) direction. Numbers on black bars indicate percentage of CW moving sporozoites; numbers in movie stills indicate time in seconds. CW moving sporozoites move at lower speed than CCW moving ones. Salivary gland sporozoites contain at least 10 microtubules as revealed by TEM of α2++‐infected salivary glands. Green arrowheads point to microtubules. Scale bar: 0.2 μm. Error bars show the full range and boxes 50% of values. Red crosses indicate the mean, and red lines indicate the median. Fisher's exact test (two‐tailed). Infectivity of sporozoites to mice decreases with decreasing numbers of microtubules and shorter microtubules. The prepatency is prolonged in parasites with a reduced sporozoite length and gliding circle diameter. See also Table 2. NMRI mice were exposed to ten mosquito bites of the respective parasite line. Numbers indicate infected mice/mice exposed to mosquito bites (left) and infected mice/mice injected with 10,000 sporozoites (right). Cartoon illustrating the various consequences of different microtubule numbers and lengths during Plasmodium sporozoite formation and tissue invasion. Sporozoites with more than 10 microtubules can enter salivary glands while salivary gland sporozoites with shorter microtubules are least infectious. Source data are available online for this figure.
IF THIS IMAGE HAS BEEN PROVIDED BY OR IS OWNED BY A THIRD PARTY, AS INDICATED IN THE CAPTION LINE, THEN FURTHER PERMISSION MAY BE NEEDED BEFORE ANY FURTHER USE. PLEASE CONTACT WILEY'S PERMISSIONS DEPARTMENT ON OR USE THE RIGHTSLINK SERVICE BY CLICKING ON THE 'REQUEST PERMISSIONS' LINK ACCOMPANYING THIS ARTICLE. WILEY OR AUTHOR OWNED IMAGES MAY BE USED FOR NON-COMMERCIAL PURPOSES, SUBJECT TO PROPER CITATION OF THE ARTICLE, AUTHOR, AND PUBLISHER.
EMBO J, Volume: 38, Issue: 15, First published: 24 May 2019, DOI: ( /embj )