Liming as a means of reducing copper toxicity in black oats

<div><p>ABSTRACT: Soils which are cultivated with grapevines have high available copper (Cu) content, which can be toxic to cover crops cohabiting vineyards, such as black oats. This study aimed to assess the effect of liming in reducing Cu toxicity in black oats grown in sandy soils. Samples of a Typic Hapludalf were collected at 0-20cm, dried and subjected to the addition of Cu (0 to 50Mg kg-1) and limestone (0, 1.5, and 3.0Mg ha-1). The soil was placed in a rhizobox and black oats were grown for 30 days. We assessed root and shoot dry matter production, copper (Cu), calcium (Ca) and magnesium (Mg) contents in the tissues; Cu content in the root symplast and apoplast, as well as Cu, carbon and pH values in the rhizosphere and bulk soil. Liming reduced Cu toxicity in black oats. Cu was preferentially accumulated in the roots, mostly in the apoplast, which may be the result of a plant tolerance mechanism to prevent the transport of Cu to the shoots.</p></div

<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

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

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

<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