Function Analysis Of SHI-Related Sequence 7(AtSRS7) And The Activity Of CAT Gene Family In Arabidopsis

In higher plants, leaf is one of crucial organs. Many genes are involved in the developmental processes of leaf morphogenesis in last ten years. Organ generation is indeterminate in plants. Leaves are determinate organs, and determinate growth is also an important characteristic of leaves. Leaf primordial arises from indeterminate SAM (Rutishauser and Sattler,1985). In higher plants, the suppression of class I KNOX genes is one process crucial for leaf morphogenesis. The difference between compound leaves and simple leaves is related to the expression pattern of class I KNOX genes. class I KNOX genes are plant-specific homeobox gene family, which are transcribed in the SAM but are specifically down-regulated in the primordia of simple leaves. On the contrary, these genes express in the primordia of compound leaves (Bharathan et al.,2002). KNAT2 is a member of class I KNOX gene family. Ectopic expression of KNAT2 could cause curly leaf (Pautot et al,2001).Many genes are involved in the regulation of class I KNOX genes in the primordia of simple leaves:ASYMMETRIC LEAVES1 (AS1), AS2, BLADE-ON-PETIOLE1 (BOP1), SERRATA (SE), PICKEL (PKL), FIE and CLF(Byrne et al.,2000; Ori et al.,2000; Semiarti et al.,2001; Prigge and Wagner, 2001; Iwakawa et al.,2002; Ha et al.,2004; Katz et al.,2004). We report here, over-expression of SRS7driven by the CaMV 35S promoter up-regulates class I KNOX family. Thus the expression of SRS7 involved in leaf development.Phytohormones play crucial roles in regulating plant development. It is suggested that the distribution and signalling of the phytohormone auxin, indole-3-acetic acid (IAA), affect many processes of polarity establishment and pattern formation in plants (Friml et al.,2003; Reinhardt et al.,2003). A crucial role for auxin in leaf initiation was displayed by a series of experiments that involved the localization of putative auxin distribution and transporters (Benkova E et al.2003; Heisler MG et al.2005; Reinhardt D et al.2003), localized exogenous auxin application (Reinhardt D et al.2000; 2003).A number of studys have implicated auxin in the formation of vascular tissues in plant organs (Carland et al.,1999; Zhong and Ye,1999; Deyholos et al.,2000; Koizumi et al.,2000). These include vascular strand formation in response to local auxin application, the effects of impaired auxin transport on vascular patterns and suggestive phenotypes of Arabidopsis auxin response mutants (Berleth and Jurgens,1993; Przemeck et al.,1996; Hamann et al.,1999; Hobbie et al.,2000).1 The SHI gene family comprises ten members that encode proteins with a RING finger-like zinc finger motif (Sandra Kuusk et al.2006). Except two conserved region, the sequence of all genes are highly divergent. The SHI-related genes are partially redundant in function and synergistically promote gynoecium, stamen and leaf development in Arabidopsis (Sandra Kuusk et al.2006).2 The sty1-1 mutant, one of SHI gene family, displays subtle morphological defects of gynoecia. Although STY2, SHI, SRS3, SRS4, SRS5, SRS7and LRP1 genes have no apparent effect on gynoecium development, the double, triple, quadruple and quintuple mutant combinations enhanced the phenotype of styl-1 gradually (Sandra Kuusk et al.2006). The protein SHI represses gibberellin responses in arabidopsis (Ingela Fridborg et al. 2001). STY1 regulates auxin homeostasis and affects apical-basal patterning of the Arabidopsis gynoecium. Auxin homeostasis or signalling might be affected by mutations in STY1 and STY2, both members of the SHI gene family (Joel J. Sohlberg et al.2006).In the present study, we identified the gain-of-function mutant of the SRS7 gene, which displayed curly leaf and dwarfism. Molecular evidence showed that accurate temporal and spatial expression of SRS7is essential for its proper functional implementation during plant development. Furthermore, we show that SRS7 induces the transcription of class I KNOX family, and that auxin homeostasis is altered in plants with ectopic expression of SRS7 and related genes. Together our data suggest that SRS7 affect leaf developmental processes by regulating class I KNOX family and auxin homeostasis.3 Leaf growth requires the function of the shoot apical meristem. (SAM) in Arabidopsis thaliana. The class 1 Knottedl-like homeobox (KNOX) genes have been identified that control SAM formation and ectopic expression of these genes cause alteration of leaf shape. The SRS7 gene, a member of SHI gene family, encodes a protein with a RING finger-like zinc finger motif. The SHI-related genes are partially redundant in function and synergistically promote gynoecium, stamen and leaf development in Arabidopsis. We identified the gain-of-function mutant of the SRS7 gene, which displayed curly leaf and dwarfism. Here, we report the expression patterns of SRS7. And it is expressed in SAM, flower and serrations of leaf but not in root. We found that constitutive and ectopic over-expression of SRS7driven by the CaMV 35S promoter up-regulates class I KNOX family and alters auxin homeostasis in the transgenic plants. Thus, ectopic SRS7 express ion alters leaf development by regulation class I KNOX family and alteration of auxin homeostasis.4 The cat2 gene, a member of catalase multi-gene family, and the cat3 gene of Arabidopsis thaliana scavenge hydrogen peroxide and participate in the development of leaf. We report here the patterns of there genes and the importance of the sites of such expression in the hydrogen peroxide scavenging and leaf development. Analysis of the leaves showed a high overall expression of CAT2, except in the vascular tissue. Compared with the CAT2 expression, CAT3 is expressed predominantly in the vasculature. Cross sections of GUS-stained leaves carrying the CAT promoter GUS fusion constructs showed localization of the CAT family and the CAT3 expression in the vascular bundle, whereas the CAT2 expression is restricted to the surrounding tissue. We have found that pCAT2::CAT3restores the curly leaf of cat2 mutant, but total activity be restored partially. And pCAT3::CAT2 is the other way round. So that showed locations and activity of cat family effect leaf development and redox homeostasis.