Interactions between Axillary Branches of Arabidopsis Ongaro Veronica , Bainbridge Katherine , Williamson Lisa , Leyser Ottoline   Molecular Plant  Volume 1, Issue 2, Pages 388-400 (March 2008) DOI: 10.1093/mp/ssn007 Copyright © 2008 The Authors. All rights reserved. Terms and Conditions

Figure 1 Two-Branch Stem Segment Assays for WT and max4 Mutant Explants. (A) Examples of two-branch explants where both branches (left), preferentially the top (t) branch (middle) or preferentially the bottom (b) branch (right) have elongated. The position of the excised apex is indicated with an asterisk. Explants were photographed at day 11. The white bar represents 1 cm. (B) Examples of two-branch explants where either the top (right) or the bottom (left) bud was excised. Arrows indicated the denuded node. The position of the excised apex is indicated with an asterisk. Explants were photographed at day 11. The white bars represent 1 cm. (C) and (D) The mean length of the longest and shortest branch after 7 and 11 d growth, respectively (n = 52). (E) The mean branch relative growth index (RGI) calculated as the length of the longer branch divided by the sum of the length of both branches. (F) and (G) The mean length after 7 or 11 d growth, respectively, of the top and bottom branches on explants where both branches were present, the top bud was removed at the start of the experiment, or the bottom bud was removed at the start of the experiment (n = 50–65). Below each bar, the presence or absence of branches is indicated in the cartoon, where an arrowhead represents a branch and a circle represents an axil from which the bud has been excised. The measured branch is indicated in red. Error bars represent the SE of the means. Molecular Plant 2008 1, 388-400DOI: (10.1093/mp/ssn007) Copyright © 2008 The Authors. All rights reserved. Terms and Conditions

Figure 2 W Stem Segment Assays for WT and max4 Mutant Explants. (A) Example of a W explant where both branches have elongated, photographed at day 11. The position of the excised apex is indicated with an asterisk. The split halves of the stem are indicated by red arrows. The white bar represents 1 cm. (B) Examples of two-branch explants where either the top (t) (right) or the bottom (b) (left) bud was excised. White arrows indicate the denuded node. The position of the excised apex is indicated with an asterisk. The split halves of the stem are indicated by red arrows. Explants were photographed at day 11. The white bars represent 1 cm. (C) and (D) The mean length of the longest and shortest branch after 7 and 11 d growth, respectively (n = 11). (E) The mean branch relative growth index (RGI) calculated as the length of the longer branch divided by the sum of the length of both branches. (F) and (G) The mean length after 7 or 11 d growth, respectively, of the top and bottom branches on W explants where both branches were present, the top bud was removed at the start of the experiment or the bottom bud was removed at the start of the experiment (n = 11–36). Below each bar, the presence of absence of branches is indicated in the cartoon, where an arrowhead represents a branch and a circle represents an axil from which the bud has been excised. The measured branch is indicated in red. (H) Two-branch explants where either the top (t) (left) or the bottom (b) (right) bud was excised. Yellow arrows indicate the stump of the branch removed from the axil. White arrows indicate accessory branches (Acc). Explants were photographed at day 11. The table shows the number of axils that developed accessory branches in WT and max4 explants. Error bars represent the SE of the means. Molecular Plant 2008 1, 388-400DOI: (10.1093/mp/ssn007) Copyright © 2008 The Authors. All rights reserved. Terms and Conditions

Figure 3 The Effect of Auxin Application. Mean branch length of WT and max4 two-branch stem segments from which one bud had been removed and replaced by auxin in lanolin paste or by lanolin. Below each bar, the presence or absence of branches is indicated in the cartoon, where an arrowhead represents a branch and a circle represents an axil from which the bud has been excised and either lanolin only (open circle) or lanolin with 1 mM NAA (shaded circle) have been applied. Error bars represent the SE of the means (n = 50–67). Molecular Plant 2008 1, 388-400DOI: (10.1093/mp/ssn007) Copyright © 2008 The Authors. All rights reserved. Terms and Conditions

Figure 4 Vascular Connections at the Node in lfy MAX4 and lfy max4. (A) Schematic representation of the vascular connections between the branch, the leaf and the stem. The orange circle indicates the key difference found between the genotypes analysed. cl, cauline leaf petiole, with midrib, which becomes the leaf trace (LT) in the stem; cb, cauline branch; s, main stem. (B) and (C) Serial transverse sections running from above the node to below the node are shown (left to right) of lfy MAX4 and lfy max4 respectively. Black arrows indicate vascular bundles in the stem of the axillary branch. White arrows indicate the point of merger of branch-derived vascular bundles and the vasculature of the stem, including the leaf trace. Yellow triangle, centre of the maim stem; yellow square, centre of stem of axillary branch. Molecular Plant 2008 1, 388-400DOI: (10.1093/mp/ssn007) Copyright © 2008 The Authors. All rights reserved. Terms and Conditions

Figure 5 Unilateral MAX Action Using DEX-Inducible MAX4 in a max4 Mutant Background. (A) and (C) DEX applied fully encircling (A) or unilaterally on (C) hypocotyls. White arrows indicate application site. Pictures were taken when plants were 12.5 weeks old. (B) and (D) Mean rosette branch number on plants when DEX is applied fully encircling (n = 10) or unilaterally to (n = 18–20) hypocotyls, respectively. For unilateral application, the branches originating on the treated and untreated side of the plants were counted separately. (E) GUS expression (black arrow) in one half of the bolting stem of a plant that had been unilaterally treated with 1 mM DEX on that side of the hypocotyl. The untreated half (white arrow) shows no GUS activity. Error bars represent the SE of the means. Molecular Plant 2008 1, 388-400DOI: (10.1093/mp/ssn007) Copyright © 2008 The Authors. All rights reserved. Terms and Conditions