Multiple types of degradative enzymes, including cathepsins of the cysteine protease family, have been implicated in the regulation of angiogenesis and invasion during cancer progression. Several cysteine cathepsins are up-regulated in a mouse model of pancreatic islet cell carcinogenesis (RIP1-Tag2), and tumor progression is impaired following their collective pharmacologic inhibition. Using null mutations of four of the implicated cysteine cathepsins, we have now dissected their individual roles in cancer development. Mutants of cathepsins B or S impaired tumor formation and angiogenesis, while cathepsin B or L knockouts retarded cell proliferation and tumor growth. Absence of any one of these three genes impaired tumor invasion. In contrast, removal of cathepsin C had no effect on either tumor formation or progression. We have identified E-cadherin as a target substrate of cathepsins B, L, and S, but not cathepsin C, potentially explaining their differential effects on tumor invasion. Furthermore, we detected analogous increases in cathepsin expression in human pancreatic endocrine neoplasms, and a significant association between increased levels of cathepsins B and L and tumor malignancy. Thus individual cysteine cathepsin genes make distinctive contributions to tumorigenesis.[Keywords: Cancer; mouse models; proteases; cysteine cathepsins; tumor microenvironment; pancreatic endocrine cancer] Supplemental material is available at http://www.genesdev.org.

SummaryFour genes of Arabidopsis (At5g20150, At2g26660, At2g45130 and At5g15330) encoding no conservative region other than an SPX domain (SYG1, Pho81 and XPR1) were named AtSPX1-AtSPX4. The various subcellular localizations of their GFP fusion proteins implied function variations for the four genes. Phosphate starvation strongly induced expression of AtSPX1 and AtSPX3 with distinct dynamic patterns, while AtSPX2 was weakly induced and AtSPX4 was suppressed. Expression of the four AtSPX genes was reduced to different extents in the Arabidopsis phr1 and siz1 mutants under phosphate starvation, indicating that they are part of the phosphate-signaling network that involves SIZ1/PHR1. Over-expression of AtSPX1 increased the transcript levels of ACP5, RNS1 and PAP2 under both phosphate-sufficient and phosphate-deficient conditions, suggesting a potential transcriptional regulation role of AtSPX1 in response to phosphate starvation. Partial repression of AtSPX3 by RNA interference led to aggravated phosphate-deficiency symptoms, altered P allocation and enhanced expression of a subset od phosphate-responsive genes including AtSPX1. Our results indicate that both AtSPX1 and AtSPX3 play positive roles in plant adaptation to phosphate starvation, and AtSPX3 may have a negative feedback regulatory role in AtSPX1 response to phosphate starvation.

The rice (Oryza sativa L.) genome contains at least six genes exclusively with an SPX (SYG1/PHO81/XPR1) domain at the N-terminal, designated as OsSPX1-6. Here we report the diverse expression patterns of the OsSPX genes in different tissues and their responses to Pi-starvation. Among them, five genes, OsSPX1, 2, 3, 5 and 6 are responsive to Pi-starvation in shoots and/or in roots. The subcellular localization analysis indicates that OsSPX1 and OsSPX2 is exclusively located in nucleus, OsSPX3 in the cytoplasm, and OsSPX4 is a membrane localization protein. OsSPX1 regulates OsSPX2, 3 and 5 at the transcription level and is positively involved in the responses of the genes to Pi-starvation. Overexpression of OsSPX3 downregulates OsSPX5 in shoots under Pi-sufficiency. OsSPX3 negatively regulates the PSI (Pi-starvation induced) gene, OsIPS1 and is involved in the responses of miR399 and OsPHO2 to Pi-starvation. Our results suggest that OsSPX1 may be a regulator involved in the transcriptions of OsSPX2, 3 and 5. OsSPX3 plays a role in OsIPS1/miR399 mediated long distance regulation on OsPHO2. Our results also indicate that OsSPX3 is involved in plant tolerance to Pi-starvation stress.

SummaryThe MADS-box transcription factor-encoding genes are expressed mainly during plant reproductive development, where they play important roles in controlling floral organ initiation and identity. Few previous reports have investigated the functions of MADS-box transcription factors expressed in vegetative tissues. Here we describe the functional characterization of a rice AG-like MADS-box protein, OsMDP1 (Oryza sativa MADSdomain-containing protein 1). A partial cDNA encoding a MADS-box domain was identified via highthroughput screening of rice brassinolide-regulated genes, and the full-length cDNA was subsequently isolated via screening of a cDNA library constructed from rice materials at tillering stage. Expression pattern analyses indicated that OsMDP1 is transcribed mainly in vegetative tissues, including the mature leaf, coleoptile, root-elongation zone, culm internode, and especially the joint region between the leaf blade and sheath. Further studies revealed that transcription of OsMDP1 is stimulated by darkness and suppressed by brassinolide treatment. OsMDP1 deficiency resulted in shortened primary roots, elongated coleoptiles and enhanced lamina joint inclinations. Moreover, transgenic plants showed hypersensitivities to exogenous brassinolide in terms of lamina joint inclination and coleoptile elongation. OsMDP1 deficiency resulted in enhanced expression of OsXTR1, which encodes xyloglucan endotransglycosylase, the cell-wall loosening enzyme necessary for cell elongation, and modulated expressions of multiple genes involved in cell signalling and gene transcription, indicating the key negative regulatory role of OsMDP1 in BR signalling.