<i>AtGRP3</i> Is Implicated in Root Size and Aluminum Response Pathways in <i>Arabidopsis</i>

<div><p>AtGRP3 is a glycine-rich protein (GRP) from <i>Arabidopsis thaliana</i> shown to interact with the receptor-like kinase AtWAK1 in yeast, <i>in vitro</i> and <i>in planta</i>. In this work, phenotypic analyses using transgenic plants were performed in order to better characterize this GRP. Plants of two independent knockout alleles of <i>AtGRP3</i> develop longer roots suggesting its involvement in root size determination. Confocal microscopy analysis showed an abnormal cell division and elongation in <i>grp3-1</i> knockout mutants. Moreover, we also show that <i>grp3-1</i> exhibits an enhanced Aluminum (Al) tolerance, a feature also described in <i>AtWAK1</i> overexpressing plants. Together, these results implicate <i>AtGRP3</i> function root size determination during development and in Al stress.</p></div

Relative expression of cell elongation and/or division molecular markers in Col and <i>grp3-1</i>.

<p>Quantitative real time PCR for <b>a</b> <i>COB</i> (At5g60920). <b>b</b> <i>KOR1</i> (At5g49720). <b>c</b> <i>CESA6</i> (At5g64740). <b>d</b> <i>POM1</i> (At1g05850). <b>e</b> <i>DWF1</i> (At3g19820). <b>f</b> <i>BRI1</i> (At4g39400). <b>g</b> <i>CDC48</i> (At3g09840). <b>h</b> <i>CYCB1;2</i> (At5g06150). <i>Error bars</i> indicate standard error. * indicates p≤ 0.05, *** indicates p≤ 0.005 and **** indicates p≤ 0.001.</p

Confocal analysis of root cells.

<p><b>a-c Division pattern of stele cells. * labels stele rows. a</b> Col wild-type. <b>b</b> <i>grp3-1</i> individual presenting normal division pattern. <b>c</b> <i>grp3-1</i> individual presenting abnormal division pattern. <b>d</b> Counting of number of stele cell rows. <b>e</b> Root diameter measurements. <b>f</b> Cell length measurements. <i>Error bars</i> indicate standard error. * indicates p≤ 0.05, ** indicates p≤ 0.01, *** indicates p≤ 0.005 and **** indicates p≤ 0.001.</p

<i>grp3-1</i> loss-of-function mutant analysis.

<p><b>a</b> Relative expression of <i>AtGRP3</i> transcripts analyzed through real-time quantitative PCR of Col and <i>grp3-1</i> mutant. <b>b</b> Summarized data for root length measurements of 2-week-old plants. <i>Error bars</i> indicate standard error. *** indicates p≤ 0.005 and **** indicates p≤ 0.001.</p