Abstract: [Objective] The SCARECROW(SCR) gene played important roles in asymmetric cell divisions to generate basic tissues in the root and shoot of plants. The structural features of SCR homologous gene PeSCR in Phyllostachys edulis were analyzed, the tissue specific expression of PeSCR was studied, the influence on PeSCR expression in roots treated with GA₃, ABA, drought and NaCl was investigated respectively, and the function was preliminarily identified by overexpressing PeSCR in Arabidopsis thaliana, which would be helpful to reveal the function of PeSCR and provide genetic resources for molecular breeding of bamboo.[Method] The sequence of SCR homologue gene PeSCR and its upstream regulatory sequence in P. edulis were retrieved from the bamboo database (BambooGDB) using bioinformatics methods. The gene structure was analyzed with Spidey and the acting elements in upstream regulatory sequence were detected using Plant CARE online softwares respectively. The tissue specific expression of PeSCR in different tissues, as well as the changes of PeSCR expression in roots treated with GA₃, ABA, drought and NaCl were analyzed using real-time quantitative PCR (qPCR). The expression vectors of sense and antisense PeSCR were constructed and transformed into A. thaliana, and the phenotype of transgenic plants was investigated to identify the function of PeSCR. [Result] A SCR homologous gene, PeSCR (GenBank No. FP094510) was obtained, the full length of cDNA was 2301 bp, including a 5' untranslated region (UTR) of 238 bp, a 3' UTR of 134 bp and an open reading frame (ORF) of 1929 bp. The genomic sequence corresponding to ORF of PeSCR was 2598 bp containing one intron of 672 bp. PeSCR encoded a protein with 642 amino acids, which had typical domains (LRⅠ, VHIID, LRⅡ, PFYRE and SAW) of GRAS family and belonged to AtSCR subfamily. PeSCR had high homology with SCRs from other monocots, among which the identities with OsSCR2 in rice and AtSCR in A. thaliana were 84.9% and 54.9%, respectively. The regulatory sequence upstream of PeSCR was 1820 bp, including many kinds of responsive elements such as cis-acting regulatory element (AuxRR-core) involved in auxin responsiveness, abscisic acid responsive element (Motif Ⅱb), MYB binding site (MBS) involved in drought-inducibility and light responsive elements, indicating that PeSCR might be regulated by hormones, drought, etc. The qPCR analysis indicated that PeSCR expressed constitutively at a high level in leaf, followed by root and stem, and the least was in sheath. The expression of PeSCR in root was inhibited by GA₃ in short time (within 1 h), but it was induced with prolonged treatment (up to 5 h). Overall, PeSCR was suppressed by exogenous ABA and NaCl, while it was induced initially and subsequently suppressed by drought. The expression of PeSCR in transgenic plants of A. thaliana was confirmed by RT-PCR. The phenotypes demonstrated that sense transgenic plants had a vigorous growth and well-developed root system compared to the wild type, while antisense transgenic plants were small and the growth of root was restrained. [Conclusion] The results indicated that the expression of PeSCR was constitutive in different tissues, and influenced by the GA₃, AAB, drought and NaCl in roots. The expression of sense PeSCR promoted the growth of transgenic plants, while that of antisense inhibited plant growth, suggesting that PeSCR might participate in regulating process of P. edulis growth and development.

Key words: Phyllostachys edulis, PeSCR, hormone, abiotic stress, gene expression, functional analysis