Hua Ling

Overexpression ofGbERF confers alteration of ethylene-responsive gene expression and enhanced resistance toPseudomonas syringae in transgenic tobacco

GbERF belongs to the ERF (ethylene responsive factor) family of transcription factors and regulates the GCC-box containing pathogen-related (PR) genes in the ethylene signal transduction pathway. To study the function of GbERF in the process of biotic stress, transgenic tobacco plants expressingGbERF were generated. Overexpression ofGbERF did not change transgenic plant’s phenotype and endogenous ethylene level. However, the expression profile of some ethylene-inducible GCC-box and non-GCC-box containing genes was altered, such asPR1b, PR2, PR3, PR4,Osmotin, CHN50, ACC oxidase and ACC synthase genes. These data indicate that the cotton GbERF could act as a transcriptional activator or repressor to regulate the differential expression of ethylene-inducible genes via GCC and non-GCCcis-elements. Moreover, the constitutive expression ofGbERF in transgenic tobacco enhanced the plant’s resistance toPseudomonas syringae pvtabaci infection. In conclusion,GbERF mediates the expression of a wide array ofPR and ethylene-responsive genes and plays an important role in the plant’s response to biotic stress.

Isolation and characterization of a homologous to lipase gene from Brassica napus

Lipase is an important lipolytic enzyme involved in plant lipid metabolism. To analyze its function and roles during seed germination and growth, a full-length cDNA encoding a homologous to lipase gene named BnLIP1 was cloned from Brassica napus, cv. Huyou 15, by rapid amplification of cDNA ends. The BnLIP1 gene had a total length of 1318 bp, with an open reading frame of 1170 bp encoding 389 amino acid residues. Sequence analysis revealed that BnLIP1 protein belonged to the GDSL family of serine esterases/lipases. In B. napus genome, BnLIP1 is represented by several copies with the length of 1601 bp, the gene comprises five exons and four introns. RT-PCR analysis indicated that BnLIP1 showed no tissue-specific expression during reproductive growth and is strongly expressed during seed germination. No expression could be detected until three days after germination, and its peak was registered at the fifth day after germination. In conclusion, BnLIP1-encoded protein is predicted to be a lipolytic enzyme widely expressed at various stages of oilseed rape germination and development.

Analysis of Arabidopsis genes encoding putative class III lipases

Triacylglycerol lipases are class of enzymes which catalyze the hydrolysis of long-chain triglycerides. They are widely found in the plant kingdom, numerous genes putatively encoding triacylglycerol lipases are sequenced but only a few of them have been characterized. Here we systematically analyzed Arabidopsis gene sequences deposited in public databases, and identified 38 putative class III lipase proteins, all of which contain a highly conserved lipase_3 domain (Pfam ID: PF01764). These 38 genes are randomly distributed on all chromosomes, and their genomic sequences consist of variable numbers of introns from zero to 13. They can be divided into four groups based on homology of protein sequences, and their potential subcellular localization is predicted to cytosol, chloroplast, mitochondria or endoplasmic reticulum. Furthermore, ten typical genes are selected to investigate their expression patterns. Most of them show weak tissue- or organ-specificity expression pattern. Several of them significantly accumulates in some tissues or organs in addition to germinated seedlings. Some of them are specifically transcribed during seed germination while others are not detected during stages of normal growth which are probably induced by stresses. In conclusion, putative Arabidopsis class III lipases display polymorphism in their sequences, gene structures and expression patterns.

Isolation and characterization of a class III homeodomain-leucine zipper-like gene from Gossypium barbadense.

Class III homeodomain-leucine zipper (HD-Zip III) genes are important plant-specific transcription factors which have key roles in different stages of vascular and interfascicular fiber differentiation. A novel HD-Zip III gene, designated GbHB1, was isolated by suppression subtraction hybridization and RACE (rapid amplification of cDNA ends) from Gossypium barbadense (sea–island cotton). The GbHB1 cDNA has a total length of 3061 bp with an open reading frame of 2508 bp, encoding a predicated polypeptide of 836 amino acids with a molecular weight of 91.6 kDa and a calculated pI of 5.93. The putative polypeptide of GbHB1 is structurally characterized by a homeodomain positioned adjacent to a leucine zipper domain, which shares high identity with other reported HD-Zip III domains. DNA gel blotting analysis shows that GbHB1 is a low-copy gene. Organ expression pattern analysis reveals that GbHB1 expressed highly in ovule and stem, followed by in root, and low in leaf and cotyledon. The result suggests that GbHB1 may play a regulatory role in cotton interfascicular fiber development.