西瓜XBCl3家族的鉴定与抗病功能分析

Characterization and functional analyses of watermelon XBCl3 family in disease resistance

XB3家族成员在拟南芥、水稻等植物的生长发育和抗逆过程中起重要作用。本文鉴定了西瓜XBCl3家族成员,并分析其基因表达模式、蛋白生化活性以及在抗病性中的可能作用。结果表明,在西瓜基因组中共有6个编码XBCl3蛋白的基因XBCl31~XBCl36,其编码蛋白均含有1个RING结构域和不同数目的锚蛋白重复序列。西瓜XBCl3基因在根、茎、叶、花等组织中呈现不同的表达模式,在MeJA、SA、ACC等植物生长调节剂处理和枯萎病菌侵染后呈现不同的诱导表达特征。XBCl34和XBCl35具有体外自我泛素化活性,而其他西瓜XBCl3蛋白则无体外自我泛素化活性。过量表达XBCl33的拟南芥植株弱化对灰霉病菌的抗性,过量表达XBCl35的拟南芥植株提高对灰霉病菌的抗性,而过量表达其他西瓜XBCl3基因的拟南芥植株不改变对灰霉病的抗性。综上,西瓜XBCl33和XBCl35分别负、正调控拟南芥植株对灰霉病的抗性,可能在西瓜抗病性中起作用。

Members in XB3 family have been shown to play roles in growth, development and stress response in plants. In the present study, we characterized the XBCl3 family in watermelon, analyzed the expression pattern and biochemical activity, and explored their involvement in disease resistance. Bioinformatics analyses identified 6 members in the watermelon XBCl3 family, namely XBCl31–XBCl36. The XBCl3 proteins in watermelon contain a typical RING domain in the C-terminal regions and ankyrin repeats motifs in the N-terminal regions. The watermelon XBCl3 genes express in root, stem, leaf and flower tissues with different patterns and also respond to plant growth regulators such as salicylic acid, methyl jasmonate and aminocyclopropane-1-carboxylicacid(an ethylene precursor) as well as to infection by Fusarium oxysporum f. sp. nievum. Biochemical assays showed that recombinant XBCl34 and XBCl35 proteins had autoubiquitination activity in vitro, while the remaining XBCl3 proteins did not have autoubiquitination activity. Overexpression of XBCl33 in transgenic Arabidopsis plants resulted in attenuated resistance while overexpression of XBCl35 led to enhanced resistance against Botrytis cinerea. However, overexpression of other XBCl3 genes including XBCl31, XBCl32, XBCL34 and XBCl36 did affect the resistance of transgenic Arabidopsis plants to B. cinerea. These data suggest that watermelon XBCl33 and XBCl35, as negative and positive regulators, respectively, are involved in modulating resistance against B. cinerea in transgenic Arabidopsis plants, implying their functions in disease resistance in watermelon.