College of Life Sciences, Shihezi University, Shihezi, 832003, China.
Center for Crop Biotechnology, College of Agriculture, Anhui Science and Technology University, Fengyang, 233100, China.
BMC Plant Biol. 2023 Sep 11;23(1):419. doi: 10.1186/s12870-023-04421-6.
Strigolactones (SLs) are a recently discovered class of plant hormones. SUPPRESSOR OF MAX2 1 (SMAX1)-like proteins, key component of the SL signaling pathway, have been studied extensively for their roles in regulating plant growth and development, such as plant branching. However, systematic identification and functional characterization of SMXL genes in cotton (Gossypium sp.), an important fiber and oil crop, has rarely been conducted.
We identified 210 SMXL genes from 21 plant genomes and examined their evolutionary relationships. The structural characteristics of the SMXL genes and their encoded proteins exhibited both consistency and diversity. All plant SMXL proteins possess a conserved Clp-N domain, P-loop NTPase, and EAR motif. We identified 63 SMXL genes in cotton and classified these into four evolutionary branches. Gene expression analysis revealed tissue-specific expression patterns of GhSMXL genes, with some upregulated in response to GR24 treatment. Protein co-expression network analysis showed that GhSMXL6, GhSMXL7-1, and GhSMXL7-2 mainly interact with proteins functioning in growth and development, while virus-induced gene silencing revealed that GhSMAX1-1 and GhSMAX1-2 suppress the growth and development of axillary buds.
SMXL gene family members show evolutionary diversification through the green plant lineage. GhSMXL6/7-1/7-2 genes play critical roles in the SL signaling pathway, while GhSMXL1-1 and GhSMXL1-2 function redundantly in growth of axillary buds. Characterization of the cotton SMXL gene family provides new insights into their roles in responding to SL signals and in plant growth and development. Genes identified in this study could be used as the candidate genes for improvement of plant architecture and crop yield.
独脚金内酯（SLs）是一类新发现的植物激素。作为 SL 信号通路的关键组成部分，SUPPRESSOR OF MAX2 1（SMAX1）类似蛋白在调控植物生长发育方面（如植物分枝）的作用已得到广泛研究。然而，棉花（Gossypium sp.）作为一种重要的纤维和油料作物，其 SMXL 基因的系统鉴定和功能特征研究甚少。
我们从 21 种植物基因组中鉴定出 210 个 SMXL 基因，并研究了它们的进化关系。SMXL 基因及其编码蛋白的结构特征既具有一致性，又具有多样性。所有植物的 SMXL 蛋白都具有保守的 Clp-N 结构域、P 环 NTP 酶和 EAR 基序。我们在棉花中鉴定出 63 个 SMXL 基因，并将这些基因分为四个进化分支。基因表达分析显示，GhSMXL 基因在组织中具有特异性表达模式，其中一些基因对 GR24 处理有上调表达。蛋白共表达网络分析表明，GhSMXL6、GhSMXL7-1 和 GhSMXL7-2 主要与生长发育相关的蛋白相互作用，而病毒诱导的基因沉默表明，GhSMAX1-1 和 GhSMAX1-2 抑制侧芽的生长和发育。
SMXL 基因家族成员在绿色植物进化过程中表现出多样化。GhSMXL6/7-1/7-2 基因在 SL 信号通路中起关键作用，而 GhSMXL1-1 和 GhSMXL1-2 在侧芽生长中具有冗余功能。对棉花 SMXL 基因家族的研究为其在响应 SL 信号和植物生长发育中的作用提供了新的见解。本研究中鉴定的基因可作为改良植物结构和作物产量的候选基因。
