丝氨酸对光呼吸基因节律的影响机制初探

A preliminary study on the mechanism of the effect of serine on the rhythm of photorespiration genes

昼夜节律是植物为适应环境而做出的反应。有研究指出,叶片内丝氨酸含量的变化能影响光呼吸基因的表达节律。影响昼夜节律的因素有很多,其中最重要的是糖和生物钟。据此,本研究比较了培养基中分别添加不同浓度(3%或5%)蔗糖和1 mmol·L^(-1) L-丝氨酸后,光呼吸基因在一天4个取样点的表达差异;分别分析了外加蔗糖和L-丝氨酸对内源丝氨酸和内源蔗糖含量的影响;并进一步分析了外源L-丝氨酸处理的野生型拟南芥叶片和羟基丙酮酸还原酶突变体(hpr1)叶片中生物钟基因的表达情况。实验结果显示,从1%到3%再到5%蔗糖处理,光呼吸基因的表达节律显示出了依赖糖浓度的规律性变化。叶片中蔗糖含量随处理浓度的升高而增加,同时这种处理能够诱导丝氨酸含量的升高,这可能与其影响了丝氨酸的合成有关,但并不能影响其代谢节律的改变。1 mmol·L^(-1)的L-丝氨酸处理也能改变光呼吸基因的表达节律,且与内源丝氨酸的代谢节律相吻合,同时外源丝氨酸处理能轻微诱导内源蔗糖的积累,这与突变体hpr1的结果类似。在培养基中同时添加1mmol·L^(-1)的L-丝氨酸和1%的蔗糖后,与只加1%蔗糖相比,生物钟基因的表达出现了较大的差异:虽然没有影响其节律的改变,但强烈诱导了PRR7和PRR9在白天的表达水平,从而轻微抑制了生物钟核心震荡基因CCA1和LHY在光照结束时的表达。同样,在hpr1突变体中,丝氨酸含量的积累对生物钟基因的表达也产生了类似的影响。

Circadian rhythm is a response of plants for adaptation to the environment.It was reported that the change of serine content in leaves affects the expression rhythm of photorespiration-related genes.During many factors affecting the circadian rhythm,sugar and biological clock are the two most important factors for regulation of diurnal genes expression.In this report,Arabidopsis thaliana wild-type（wt） growing in plate containing 1%,3% or 5% sucrose,or 1% sucrose plus 1 mmol·L-1 L-serine,and hpr1 mutant plants growing in 1% sucrose plate were placed in normal air under a（10/14） h day/night regime.Leaf samples were harvested at four time points of a day for the analysis of expression patterns of photorespiration-related genes.At the same points,the effects of external sucrose and L-serine on levels of endogenous serine and sucrose were also analyzed,and the expression rhythms of circadian-associated genes in the wt with L-serine treatment and hpr1 mutant were further compared.It was shown that incubation with different amounts of sucrose（1%,3% and 5%） could lead to the accumulated serine depending on the amounts of sucrose and a regular change on photorespiration-related genes.Besides,treatments also caused the endogenous sucrose significantly increased,which may be related to the synthesis of serine,but it could not alter metabolic rhythm of serine.One mmol·L-1 serine treatment altered the accumulation rhythm of endogenous serine,which was in consistence with the expressing rhythm of photorespiration-related genes.Besides,it also induced a slight accumulation of endogenous sucrose,and those alterations were agreement with those in hpr1 mutant.One mmol·L-1 L-serine supplementation in the growth medium induced significant changes of the expression levels of clock-related genes.Although the expression rhythms of genes were not changed,external L-serine supply strongly induced the expression of PRR7 and PRR9,which consequently slightly inhibited the expression of LHY and CCA1.The hpr1 mutant plants showed similar changes.