近日，華中農(nóng)業(yè)大學(xué)果蔬園藝作物種質(zhì)創(chuàng)新與利用全國重點實驗室、湖北洪山實驗室柑橘逆境應(yīng)答與品質(zhì)調(diào)控研究團隊研究成果以“The CtrCBL1/CtrCIPK6 Complex of Citrus Phosphorylates CtrBBX32 to Regulate CtrSTP1-mediated Sugar Accumulation and Cold Tolerance”為題在Advacned Science發(fā)表。研究揭示了鈣信號調(diào)控模塊CtrCBL1/CtrCIPK6-CtrBBX32 促進根系糖轉(zhuǎn)運蛋白CtrSTP1高表達，從而提升可溶性糖積累、增強柑橘抗寒性的分子路徑，為理解逆境下植物碳源分配和根系糖運輸積累提供了新見解，也為改良植物抗寒性提供關(guān)鍵功能基因。

 

　　溫度是影響植物生長發(fā)育的關(guān)鍵環(huán)境因素，低溫對作物產(chǎn)量和地理分布造成重要限制。柑橘是我國南方重要的果樹，喜溫畏寒，冬季低溫常對柑橘產(chǎn)業(yè)造成威脅。因此，解析柑橘抗寒應(yīng)答機制，提升其抗寒能力是重要的產(chǎn)業(yè)需求。提高可溶性糖含量是植物應(yīng)對低溫逆境的重要策略，而多年生果樹常采用嫁接栽培，砧木根系如何響應(yīng)低溫增強可溶性糖積累和抗寒性的機制仍知之甚少。

 

　　本研究通過挖掘柑橘砧木枳低溫處理轉(zhuǎn)錄組篩選到一個被顯著誘導(dǎo)的糖轉(zhuǎn)運蛋白編碼基因CtrSTP1，并且其在根皮層薄壁細胞中特異高表達。亞細胞定位及底物吸收實驗表明CtrSTP1蛋白定位于細胞膜且具有己糖轉(zhuǎn)運功能。轉(zhuǎn)基因材料生理表型證明，CtrSTP1高表達可促進低溫下可溶性糖積累并提升柑橘抗寒能力，沉默其表達則表型相反，說明CtrSTP1是柑橘砧木應(yīng)對低溫的重要基因。

 

　　利用CtrSTP1啟動子為誘餌進行酵母單雜交篩庫，挖掘到其上游的兩個轉(zhuǎn)錄因子CtrZAT10和CtrBBX32。生化實驗和轉(zhuǎn)基因材料生理表型證明CtrZAT10作為轉(zhuǎn)錄激活子促進CtrSTP1的表達，增強枳的耐寒性；而CtrBBX32則作為轉(zhuǎn)錄抑制子同時降低CtrSTP1、CtrZAT10的轉(zhuǎn)錄水平，破壞枳的耐寒性。為進一步闡明低溫下植物如何打破CtrBBX32的轉(zhuǎn)錄抑制效應(yīng)，通過酵母雙雜交篩選到與CtrBBX32互作的鈣信號響應(yīng)蛋白激酶 CtrCIPK6，該激酶可以磷酸化CtrBBX32的絲氨酸（Ser）108位點，促進低溫環(huán)境下的蛋白降解，解除其對CtrSTP1的轉(zhuǎn)錄抑制作用。以上內(nèi)容闡明了正、負轉(zhuǎn)錄因子及鈣信號成員調(diào)控糖轉(zhuǎn)運蛋白表達的分子路徑，系統(tǒng)解析了低溫環(huán)境下柑橘砧木根系糖積累和穩(wěn)態(tài)調(diào)控的創(chuàng)新機制，為柑橘抗寒改良提供重要參考和理論依據(jù)。

 

　　華中農(nóng)業(yè)大學(xué)園藝林學(xué)學(xué)院博士研究生商祥明為論文第一作者，劉繼紅教授、李春龍教授為論文共同通訊作者。本研究得到了國家重點研發(fā)計劃項目、國家自然科學(xué)基金項目等項目資助。

 

　　論文鏈接：https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202508372

 

　　英文摘要

 

　　Sugar accumulation is a crucial adaptive strategy for plant cold tolerance, yet its regulatory mechanisms in the roots under cold conditions remain largely unclear. Here, we identified a cold-inducible sugar transporter protein （CtrSTP1）， which was highly expressed in the roots of trifoliate orange （Citrus trifoliata L.）。 CtrSTP1 functioned positively in cold tolerance by facilitating sugar accumulation in the roots. Two transcription factors, CtrBBX32 and CtrZAT10, bound to the CtrSTP1 promoter, with CtrBBX32 acting as transcriptional repressor and CtrZAT10 as activator. CtrBBX32 also suppressed CtrZAT10 expression. Accordingly, CtrBBX32 and CtrZAT10 acted as negative and positive regulators, respectively, of cold tolerance by modulating CtrSTP1 expression. Moreover, CtrCBL1 and CtrCIPK6 formed a complex to phosphorylate CtrBBX32 and promoted its protein degradation, leading to relief of CtrBBX32-mediated repression on CtrZAT10 and CtrSTP1. Further transgenic evidence confirmed that CtrCIPK6 played a positive role in cold tolerance through modulating the sugar pathway. Taken together, these findings uncover a novel regulatory module composed of CtrCBL1/CtrCIPK6-CtrBBX32 that controls cold-induced sugar accumulation by directly or indirectly （via CtrZAT10） modulating the expression of the root-localized CtrSTP1. Our work provides valuable knowledge to advance the understanding of sugar transport and homeostasis in the roots when plants are exposed to adverse environments.