关键词: 水稻, 根系, 高浓度CO₂, 镉胁迫, 淀粉-蔗糖代谢响应, 差异表达lncRNA

Abstract: In order to explore the regulatory mechanism of starch⁃sucrose metabolism in rice seedling roots under elevated CO₂（EC），cadmium（Cd） stress，and their combined stress，four treatments were set up，including ambient CO₂ control（AC，400 μmol/mol CO₂ + 0 μmol/L CdCl₂），single Cd stress（Cd，400 μmol/mol CO₂ + 150 μmol/L CdCl₂），single elevated CO₂（EC，800 μmol/mol CO₂ + 0 μmol/L CdCl₂），and combined EC and Cd stress（EC+Cd，800 μmol/mol CO₂ + 150 μmol/L CdCl₂）. The contents of starch and sucrose as well as the activities of key metabolic enzymes in rice seedling roots were studied.Differentially expressed long non⁃coding RNAs（DE⁃lncRNAs）of different comparison groups were screened，and their potential cis⁃regulatory target genes were predicted.The cis⁃target genes were further intersected with key enzyme⁃encoding genes involved in the starch⁃sucrose metabolic pathway to analyze the regulatory patterns. The results showed that compared with the AC treatment，Cd treatment reduced the root starch content，significantly increased the sucrose content，significantly improved the activities of invertase（INV），β⁃glucosidase（β⁃Glu），sucrose synthase（SUS），sucrose phosphate synthase（SPS），α⁃amylase（α⁃AMY） and isoamylase（ISA），and significantly inhibited the activities of hexokinase（HXK）and β⁃amylase（β⁃AMY），thereby promoting starch degradation and sucrose accumulation；EC treatment decreased the starch content，increased the sucrose content，but both changes were not significant，significantly decreased the activities of INV and β⁃Glu，and significantly increased the activities of HXK，SUS and α⁃AMY；EC+Cd treatment significantly decreased the starch content and activities of HXK and β⁃AMY，and significantly increased the sucrose content and activities of INV，β⁃Glu，SUS，α⁃AMY and ISA.Compared with Cd treatment，EC+Cd treatment decreased the contents of starch and sucrose，but the difference was not significant，significantly increased the activities of INV，β⁃Glu and β⁃AMY，and significantly suppressed the activities of SUS，SPS and ISA.Analysis of DE⁃lncRNAs and their cis⁃target genes indicated that，compared with AC treatment，under Cd treatment，MSTRG.18576.11 was upregulated，and positively regulated its target gene INV（Os04g0535600），thereby increasing INV activity； MSTRG. 4063.2 and its target gene Os01g094010 were synchronously downregulated，leading to a reduction in HXK activity； MSTRG.28469.1 and MSTRG.18188.1 were downregulated，and positively regulated their target genes Os08g0509400 and Os04g0474500，respectively，thereby improving β⁃Glu activity； MSTRG. 12325. 1 and MSTRG. 26969.1 were upregulated，and negatively regulated their respective target genes Os02g0712600 and Os08g012400，thereby increasing α⁃AMY activity. Under EC treatment，MSTRG.18576.11 and its target gene were synchronously downregulated to reduce INV activity； MSTRG. 4063.2 was downregulated，and negatively regulated its target gene，resulting in increase of HXK activity； MSTRG. 18188. 1 and MSTRG. 28469.1 were synchronously downregulated along with their target genes，which reduced β⁃Glu activity；MSTRG. 12325.1 was upregulated，negatively regulating its target gene，while MSTRG.26969.1 was upregulated，positively regulating its target gene，the positive regulatory effect of MSTRG. 26969. 1 was dominant，and ultimately increased α⁃AMY activity. Under EC+Cd treatment，MSTRG. 18576. 11 and its target gene were synchronously upregulated to elevate INV activity； MSTRG. 4063.2 and its target gene were synchronously downregulated to decrease HXK activity；MSTRG. 28469.1 and MSTRG.18188.1 were synchronously downregulated along with their target genes，which increased β⁃Glu activity；MSTRG. 12325.1 was upregulated，negatively regulating its target gene，MSTRG. 26969.1 was upregulated，positively regulating its target gene，and the positive regulatory effect of MSTRG. 26969.1 played a dominant role，thereby increasing α⁃AMY activity. Compared with Cd treatment，under EC+Cd treatment，MSTRG.18576.11 was upregulated，and positively regulated its target gene，further increasing INV activity；MSTRG. 4063.2 was downregulated，and negatively regulated its target gene，leading to elevated HXK activity；MSTRG. 28469.1 was upregulated，and positively regulated its target gene to promote the increase of β⁃Glu activity；MSTRG. 18188.1 showed no significant expression change，but still modulated β⁃Glu activity via its target gene；MSTRG. 12325.1 and MSTRG. 26969.1 regulated their target genes through negative and positive modulation，respectively，thereby maintaining the stability of α⁃AMY activity.

Key words: Rice, Roots, Elevated CO₂ concentration, Cadmium stress, Response of starch?sucrose metabolism, Differentially expressed lncRNA