Coordinated activation of cellulose and repression of lignin biosynthesis pathways in rice.
Background Eucalyptus forests are a competitive and efficient alternative to convert carbon from the atmosphere in cellulose, an important source for paper manufacture and bioenergy production. To obtain transgenic Eucalyptus with important traits improved it is necessary to make modifications in genes that affect the final phenotype. One interesting gene that follows this requisite was recently found: this is the AtSHN2 gene (Arabidopsis thaliana SHINE 2). AtSHN2 codifies to a Transcription Factor known as “Arabidopsis SHINE/WAX INDUCER”. Instead of inducing drought tolerance in transgenic rice (Oryza sativa), AtSHN2 overexpression causes: i) 34% increase in the cellulose content; ii) 45% reduction in lignin content and iii) increase in wood digestibly (elevated S:G ratio) with no compromise in plant strength and performance . The discovery of AtSHN2 function in plant cell wall formation, led Ambavaram and collaborators  to perform other studies and ultimately to propose the following model: AtSHN2 regulates positively MYB transcription factors (TF) related to cellulose synthesis and it downregulates MYBTF’s related to lignin formation. At the same time, SHINE can repress NAC TFthat controls MYB expression. As a consequence of the interesting phenotype achieved through AtSHN2 overexpression in rice, this work focused on the identification and analyses of AtSHN orthologues in Eucalyptus. Bioinformatics tools were used to search for AtSHN similar genes in Eucalyptus. Moreover, the expression profile of the corresponding genes in Eucalyptus was evaluated to prove their role as AtSHN. To carry it on, the expression experiments were done with flower, leaf and xylem. If the Eucalyptus putativeSHINE’s has the same function of the AtSHN’s,, gene expression in flower tissues will be the highest . This is because it is known that AtSHN’s genes are preferentially expressed in abscission and dehiscence zones, a phenomenon that usually occurs in lots of flower tissues.