NOVELTY - An isolated polypeptide having xylanase activity e.g. polypeptide having at least 90% sequence identity to specific mature polypeptide; polypeptide encoded by a polynucleotide that hybridizes under at least very high stringency conditions with specific mature polypeptide coding sequence or its cDNA sequence or full-length complement; or polypeptide encoded by polynucleotide having at least 90% sequence identity to the specific mature polypeptide coding sequence or its cDNA sequence is new.    USE - For producing transgenic plant, plant part or plant cell; for producing a mutant of a parent cell; for producing a protein; for producing a fermentation product; for fermenting cellulosic or xylan-containing material (all claimed); for degrading a cellulosic or xylan-containing material; for saccharifing the cellulosic or xylan-containing material to fermentable sugars and to convert the fermentable sugars to many useful fermentation products, e.g. fuel (ethanol, n-butanol, isobutanol, biodiesel, jet fuel) and/or platform chemicals (e.g. acids, alcohols, ketones, gases or oils).    ADVANTAGE - The isolated polypeptide ferment cellulosic or xylan-containing material; degrades cellulosic or xylan-containing material; saccharifes the cellulosic or xylan-containing material to fermentable sugars and convert the fermentable sugars to many useful fermentation products, e.g. fuel such as ethanol. The isolated polypeptide improves cellulolytic enzyme composition through supplementation with additional enzymes to increase efficiency and provide cost-effective enzyme solutions for degradation of lignocellulose.    DETAILED DESCRIPTION - An isolated polypeptide having xylanase activity, selected from a) a polypeptide having at least 90% sequence identity to the mature polypeptide of (SEQ ID NO: 2) as available on WIPO website (Sequences not defined here may be found at ftp://ftp.wipo.int/pub/published pct sequences/publication); b) polypeptide encoded by a polynucleotide that hybridizes under at least very high stringency conditions with the mature polypeptide coding sequence of (SEQ ID NO: 1) as available on WIPO website (Sequences not defined here may be found at ftp://ftp.wipo.int/pub/published pct sequences/publication) or its cDNA sequence or full-length complement; c) polypeptide encoded by a polynucleotide having at least 90% sequence identity to the mature polypeptide coding sequence of the (SEQ ID NO: 1) or its cDNA sequence; d) a variant of the mature polypeptide of the (SEQ ID NO: 2) comprising a substitution, deletion, and/or insertion at at least one position; and e) fragment of the polypeptide of (a), (b), (c), or (d) that has xylanase activity is new. INDEPENDENT CLAIMS are included for the following:    (1) an isolated polynucleotide encoding the polypeptide;    (2) a recombinant host cell comprising the polynucleotide operably linked to at least one control sequence that direct the production of the polypeptide;    (3) producing the polypeptide;    (4) a transgenic plant, plant part or plant cell transformed with the polynucleotide encoding the polypeptide;    (5) producing a mutant of a parent cell involving: inactivating the polynucleotide encoding the polypeptide, which results in the mutant producing less of the polypeptide than the parent cell;    (6) a double-stranded inhibitory RNA (dsRNA) molecule comprising subsequence of the polynucleotide, where optionally the dsRNA is a siRNA or a miRNA molecule;    (7) inhibiting the expression of a polypeptide having xylanase activity in a cell, involving: administering to the cell or expressing in the cell the double-stranded inhibitory RNA (dsRNA) molecule;    (8) an isolated polynucleotide encoding a signal peptide comprising or consisting of amino acids 1-18 of the (SEQ ID NO: 2);    (9) producing a protein involving: cultivating a recombinant host cell comprising a gene encoding a protein operably linked to the polynucleotide, where the gene is foreign to the polynucleotide encoding the signal peptide, under conditions conducive for production of the protein;    (10) degrading a cellulosic or xylan-containing material involving: treating the cellulosic or xylan-containing material with an enzyme composition in the presence of the polypeptide having xylanase;    (11) producing a fermentation product involving: saccharifying a cellulosic or xylan-containing material with an enzyme composition in the presence of the polypeptide having xylanase activity; fermenting the saccharified cellulosic or xylan-containing material with at least one fermenting microorganisms to produce the fermentation product; and recovering the fermentation product from the fermentation;    (12) fermenting a cellulosic or xylan-containing material involving: fermenting the cellulosic or xylan-containing material with at least one fermenting microorganisms, where the cellulosic or xylan-containing material is saccharified with an enzyme composition in the presence of the polypeptide having xylanase activity; and    (13) a whole broth formulation or cell culture composition comprising the polypeptide.