Zhu Keming, Li Nannan, Zheng Xiangfeng, Sarwar Rehman, Li Yulong, Cao Jun, Wang Zheng, Tan Xiaoli
School of Life Sciences, Jiangsu University, Zhenjiang, China.
Chongqing Key Lab of Bioresource for Energy, College of Resources and Environment, Southwest University, Chongqing, China.
Biotechnol Biofuels Bioprod. 2023 Jan 6;16(1):3. doi: 10.1186/s13068-022-02254-3.
Chlorophyll is a very important pigment involved in photosynthesis, while plant acyl-CoA biosynthesis is derived from plastid-localized fatty acids (FAs). Until now, the regulation of the acyl-CoA pathway for chlorophyll biosynthesis is still unknown.
Here, we identified a long-chain acyl-CoA synthetase (LACS) gene BnLACS9 from Brassica napus. BnLACS9 complemented a LACS-deficient yeast strain YB525, which indicated that BnLACS9 has the LACS function. BnLACS9 was localized in the chloroplast envelope membrane, while mainly expressed in young leaves and flowers. Overexpression of BnLACS9 in Nicotiana benthamiana resulted in an increase in total CoA and MGDG content. In B. napus with overexpression of BnLACS9, the number of chloroplast grana lamellae and the chlorophyll content, as well as the MGDG and DGDG contents, increased compared to wild type. The net photosynthetic rate, dry weight of the entire plant and oil content of seeds increased significantly, accompanied by an increase in chlorophyll content. Transcriptome analysis revealed that overexpression of BnLACS9 improved the pathway of acyl-CoA biosynthesis and further improved the enzymes in the glycolipid synthesis pathway, while acyl-CoA was the substrate for glycolipid synthesis. The increased glycolipids, especially MGDG and DGDG, accelerated the formation of the chloroplast grana lamellae, which increased the number of chloroplast thylakoid grana lamella and further lead to increased chlorophyll content.
In the present study, we demonstrated that BnLACS9 played a crucial role in glycolipids and chlorophyll biosynthesis in B. napus. The results also provide a new direction and theoretical basis for the improvement of the agronomic traits of plants.
叶绿素是参与光合作用的一种非常重要的色素，而植物酰基辅酶A生物合成源自质体定位的脂肪酸（FAs）。到目前为止，叶绿素生物合成中酰基辅酶A途径的调控仍不清楚。
在此，我们从甘蓝型油菜中鉴定出一个长链酰基辅酶A合成酶（LACS）基因BnLACS9。BnLACS9互补了一个LACS缺陷型酵母菌株YB525，这表明BnLACS9具有LACS功能。BnLACS9定位于叶绿体被膜，主要在幼叶和花中表达。在本氏烟草中过表达BnLACS9导致总辅酶A和单半乳糖基二酰甘油（MGDG）含量增加。在过表达BnLACS9的甘蓝型油菜中，与野生型相比，叶绿体基粒片层数量、叶绿素含量以及MGDG和双半乳糖基二酰甘油（DGDG）含量均增加。净光合速率、整株植物干重和种子含油量显著增加，同时叶绿素含量也增加。转录组分析表明，BnLACS9的过表达改善了酰基辅酶A生物合成途径，并进一步改善了糖脂合成途径中的酶，而酰基辅酶A是糖脂合成的底物。糖脂增加，尤其是MGDG和DGDG，加速了叶绿体基粒片层的形成，增加了叶绿体类囊体基粒片层数量，进而导致叶绿素含量增加。
在本研究中，我们证明了BnLACS9在甘蓝型油菜糖脂和叶绿素生物合成中起关键作用。这些结果也为改善植物农艺性状提供了新的方向和理论基础。
