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Liu, Yunxia,Xu, Fuyu,Gou, Jiqing,Al-Haddad, Jameel,Telewski, Frank W,Bae, Hyeun-Jong,Joshi, Chandrashekhar P Heron Pub 2012 Tree physiology Vol.32 No.11
<P>All known orthologs of a secondary wall-associated cellulose synthase (CesA) gene from Arabidopsis, AtCesA8, encode CesA proteins with two consecutive methionines at their N-termini (MM or 2M). Here, we report that these 2Ms in an aspen ortholog of AtCesA8, PtdCesA8A, are important for maintaining normal wood cellulose biosynthesis in aspen trees. Overexpression of an altered PtdCesA8A cDNA encoding a PtdCesA8A protein missing one methionine at the N-terminus (1M) in aspen resulted in substantial decrease in cellulose content and caused negative effects on wood strength, suggesting that both methionines are essential for proper CesA expression and function in developing xylem tissues. Transcripts from a pair of paralogous native PtdCesA8 genes, as well as introduced PtdCesA8A:1M transgenes were significantly reduced in developing xylem tissues of transgenic aspen plants, suggestive of a co-suppression event. Overexpression of a native PtdCesA8A cDNA encoding a CesA protein with 2Ms at the N-terminus did not cause any such phenotypic changes. These results suggest the importance of 2Ms present at the N-terminus of PtdCesA8A protein during cellulose synthesis in aspen.</P>
Al-Haddad, Jameel M.,Kang, Kyu-Young,Mansfield, Shawn D.,Telewski, Frank W. Oxford University Press 2013 Tree physiology Vol.33 No.4
<P>The effect of altering the expression level of the <I>F5H</I> gene was investigated in three wood tissues (normal, opposite and tension wood) in 1-year-old hybrid poplar clone 717 (<I>Populus tremula × Populus alba</I> L.), containing the <I>F5H</I> gene under the control of the <I>C4H</I> promoter. Elevated expression of the <I>F5H</I> gene in poplar has been previously reported to increase the percent syringyl content of lignin. The wild-type and three transgenic lines were inclined 45° for 3 months to induce tension wood formation. Tension and opposite wood from inclined trees, along with normal wood from control trees, were analyzed separately for carbohydrates, lignin, cellulose crystallinity and microfibril angle (MFA). In the wild-type poplar, the lignin in tension wood contained a significantly higher percentage of syringyl than normal wood or opposite wood. However, there was no significant difference in the percent syringyl content of the three wood types within each of the transgenic lines. Increasing the <I>F5H</I> gene expression caused an increase in the percent syringyl content and a slight decrease in the total lignin in normal wood. In tension wood, the addition of a gelatinous layer in the fiber walls resulted in a consistently lower percentage of total lignin in the tissue. Acid-soluble lignin was observed to increase by up to 2.3-fold in the transgenic lines. Compared with normal wood and opposite wood, cell wall crystallinity in tension wood was higher and the MFA was smaller, as expected, with no evidence of an effect from modifying the syringyl monomer ratio. Tension wood in all the lines contained consistently higher total sugar and glucose percentages when compared with normal wood within the respective lines. However, both sugar and glucose percentages were lower in the tension wood of transgenic lines when compared with the tension wood of wild-type trees. Evaluating the response of trees with altered syringyl content to gravity will improve our understanding of the changes in cell wall chemistry and ultrastructural properties of normal, opposite and tension wood in plants.</P>
Kang, Jin-Ho,Campos, Marcelo L.,Zemelis-Durfee, Starla,Al-Haddad, Jameel M.,Jones, A. Daniel,Telewski, Frank W.,Brandizzi, Federica,Howe, Gregg A. Oxford University Press 2016 Journal of experimental botany Vol.67 No.18
<P>Trichomes are epidermal structures that provide a first line of defense against arthropod herbivores. The recessive <I>hairless</I> (<I>hl</I>) mutation in tomato (<I>Solanum lycopersicum</I> L.) causes severe distortion of trichomes on all aerial tissues, impairs the accumulation of sesquiterpene and polyphenolic compounds in glandular trichomes, and compromises resistance to the specialist herbivore <I>Manduca sexta</I>. Here, we demonstrate that the tomato <I>Hl</I> gene encodes a subunit (SRA1) of the highly conserved WAVE regulatory complex that controls nucleation of actin filaments in a wide range of eukaryotic cells. The tomato <I>SRA1</I> gene spans a 42-kb region containing both <I>Solyc11g013280</I> and <I>Solyc11g013290</I>. The <I>hl</I> mutation corresponds to a complex 3-kb deletion that removes the last exon of the gene. Expression of a wild-type <I>SRA1</I> cDNA in the <I>hl</I> mutant background restored normal trichome development, accumulation of glandular trichome-derived metabolites, and resistance to insect herbivory. These findings establish a role for <I>SRA1</I> in the development of tomato trichomes and also implicate the actin-cytoskeleton network in cytosolic control of specialized metabolism for plant defense. We also show that the brittleness of <I>hl</I> mutant stems is associated with altered mechanical and cell morphological properties of stem tissue, and demonstrate that this defect is directly linked to the mutation in <I>SRA1</I>.</P>