Importance of two consecutive methionines at the N-terminus of a cellulose synthase (PtdCesA8A) for normal wood cellulose synthesis in aspen

Abstract

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.

Nitrogen-driven stem elongation in poplar is linked with wood modification and gene clusters for stress, photosynthesis and cell wall formation

“…In complex 1 the highest node connectivity was 21 to 30 edges per node, but the maximum number of nodes was in the category with the lowest connectivity (1 to 5 edges per node) (Figure 3 ). The genes with the highest connectivity included a homolog to PAD4 , a lipase involved in plant immune response and fitness [ 45 ] in complex 1 (26 edges), a scarcely defined nucleotide binding protein with functions in chloroplast metabolism [ 46 ] in complex 2 (48 edges) and a cellulose synthase [ 47 ] in complex 3 (37 edges) (Additional file 4 : Table S3).…”

Molecular cloning of the tomato Hairless gene implicates actin dynamics in trichome-mediated defense and mechanical properties of stem tissue

“…Green stems from 3-month-old plants were cut into segments that were more than 14 times longer than their diameters, as required for the bending test ( Niklas, 1992 ; Pruyn et al , 2000 ; Liu et al , 2012 ) and in compliance with the testing standard ASTM D143 (1994). The four-point bending test was conducted at room temperature by loading the stem segments to failure using a United ® universal testing machine (Model SFM-20, United Calibration Corporation, USA) fitted with a 20 lb load cell (89 Newton) and at a crosshead rate of 30mm min −1 .…”

Functional understanding of secondary cell wall cellulose synthases in Populustrichocarpa via the Cas9/gRNA‐induced gene knockouts

“…Proteomic data have implied that CesA4, 7A/B and 8A/B, and CesA1A/B, 3C/D and 6E/F assemble into two types of Populus CSCs, which might contribute simultaneously to cellulose biosynthesis in wood SCWs (Song et␣al ., 2010 ; Xi et␣al ., 2017 ). Overexpression of an aspen mutant CesA8 lacking one of the N‐terminal methionines unexpectedly resulted in a silencing of the transgene and revealed the role of CesA8 in vertical tree growth (Joshi et␣al ., 2011 ; Liu et␣al ., 2012 ). Most recently, SCW CesA stoichiometry in developing aspen xylem was suggested by quantitative proteomics to be 3 : 2 : 1 (Zhang et␣al ., 2018 ).…”