State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University. Guangzhou, 510642, China.
Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architectures, South China Agricultural University. Guangzhou, 510642, China.
J Exp Bot. 2022 Jun 2;73(11):3477-3495. doi: 10.1093/jxb/erac066.
The production of Arabidopsis seed mucilage involves complex polysaccharide biosynthetic pathways and developmental processes in seed epidermal cells. Although the polysaccharide components of Arabidopsis seed mucilage have been identified, their regulatory mechanism requires further investigation. Here, we show that Class II KNOX gene family members KNAT3 and KNAT7 play an essential role in regulating mucilage production in the early developmental stages of Arabidopsis seeds. Double mutant knat3knat7 resulted in defective seed mucilage production and columellae formation, whereas knat3 showed a normal phenotype compared with wild type, and the mucilage thickness in knat7 was slightly disturbed. Rhamnogalacturonan I (RG-I) and its biosynthetic substrates galacturonic acid and rhamnose were reduced in both the adherent and soluble mucilage of knat3knat7. Comparative transcriptome analysis on whole seeds suggested that polysaccharide, glucosinolate and anthocyanin biosynthetic pathways were specifically repressed in knat3knat7. Transient co-expression of KNAT3 and KNAT7 with promoter regions of candidate genes in Arabidopsis protoplasts revealed that both KNAT3 and KNAT7 act as positive regulators of the RG-I biosynthetic gene MUCILAGE-MODIFIED 4 (MUM4, AT1G53500). Collectively, our results demonstrate that KNAT3 and KNAT7 are multifunctional transcription factors in secondary cell wall development and redundantly modulate mucilage biosynthesis in Arabidopsis seeds.
拟南芥种子黏液的产生涉及到种子表皮细胞中复杂的多糖生物合成途径和发育过程。尽管已经鉴定出拟南芥种子黏液的多糖成分，但它们的调控机制仍需要进一步研究。在这里，我们表明 II 类 KNOX 基因家族成员 KNAT3 和 KNAT7 在调节拟南芥种子早期发育阶段的黏液产生中起着重要作用。knat3knat7 双突变体导致黏液产生和柱状细胞形成缺陷，而与野生型相比，knat3 表现出正常的表型，并且 knat7 中的黏液厚度略有紊乱。在 knat3knat7 中，鼠李半乳糖醛酸聚糖 I（RG-I）及其生物合成底物半乳糖酸和鼠李糖减少，无论是在黏附性黏液还是可溶性黏液中均如此。对整个种子的比较转录组分析表明，多糖、硫代葡萄糖苷和花色素苷生物合成途径在 knat3knat7 中被特异性抑制。在拟南芥原生质体中转瞬共表达 KNAT3 和 KNAT7 及其候选基因的启动子区域表明，KNAT3 和 KNAT7 均作为 RG-I 生物合成基因 MUCILAGE-MODIFIED 4（MUM4，AT1G53500）的正调控因子发挥作用。总之，我们的结果表明，KNAT3 和 KNAT7 是次生细胞壁发育中的多功能转录因子，在拟南芥种子中冗余地调节黏液生物合成。
