Table 1_Genome-wide analysis of bHLH transcription factor family reveals their involvement in kernel development and biotic stress responses in Chinese chestnut.xlsx

IntroductionThe basic helix-loop-helix (bHLH) transcription factor family plays crucial roles in plant growth, development, and responses to environmental stresses. However, a systematic characterization of bHLH genes in Castanea mollissima has been lacking.
MethodsWe performed a genome-wide identification of bHLH genes in C. mollissima, followed by phylogenetic, structural, motif, chromosomal distribution, and cis-element analyses. Co-expression network analysis and transcriptomic profiling under Dryocosmus kuriphilus infestation were conducted, and representative genes were validated using qRT-PCR across seed developmental stages.
ResultsA total of 124 non-redundant bHLH genes (CmbHLHs) were identified and classified into eight subfamilies, consistent with conserved gene structures and motif compositions, particularly motif-1 and motif-2 of the canonical bHLH domain. Chromosomal mapping revealed non-random distribution and tandem duplication events. Promoter analysis indicated enrichment of cis-elements responsive to stress, hormone signaling, and developmental regulation. Co-expression analysis highlighted hub genes, including CmbHLH82 and CmbHLH57, with potential regulatory functions. Transcriptomic data showed that most CmbHLHs were downregulated under D. kuriphilus infestation, notably CmbHLH63 and CmbHLH51. qRT-PCR confirmed the dynamic expression of five selected genes during seed development.
DiscussionThese findings provide the first comprehensive overview of the bHLH gene family in Chinese chestnut. The results highlight candidate genes potentially involved in development and insect resistance, thereby laying a foundation for future functional and breeding studies.

引言 基本螺旋-环-螺旋（basic helix-loop-helix, bHLH）转录因子家族在植物生长、发育以及环境胁迫响应中发挥关键作用。然而，目前针对板栗（Castanea mollissima）的bHLH基因尚未开展系统性特征分析。
方法 本研究对板栗（C. mollissima）全基因组范围内的bHLH基因进行鉴定，随后开展系统发育、基因结构、基序（motif）、染色体分布以及顺式作用元件分析。同时，本研究对栗瘿蜂（Dryocosmus kuriphilus）侵染条件下的样本开展了共表达网络分析与转录组谱分析，并选取代表性基因，通过qRT-PCR验证其在种子发育不同阶段的表达情况。
结果 本研究共鉴定得到124个非冗余bHLH基因（命名为CmbHLHs），并将其划分为8个亚家族，该分类结果与保守的基因结构及基序组成一致，尤其是典型bHLH结构域的基序1与基序2。染色体定位分析显示，这些基因呈非随机分布且存在串联重复事件。启动子分析表明，其调控区域富集了响应胁迫、激素信号转导以及发育调控的顺式作用元件。共表达分析筛选得到核心枢纽基因，包括CmbHLH82与CmbHLH57，二者具备潜在的调控功能。转录组数据显示，多数CmbHLHs在栗瘿蜂（D. kuriphilus）侵染后表达量下调，其中CmbHLH63与CmbHLH51的表达变化最为显著。qRT-PCR验证了5个所选基因在种子发育过程中的动态表达模式。
讨论 本研究首次对板栗（Castanea mollissima）的bHLH基因家族进行了全面系统的特征解析。研究结果筛选得到了可能参与植物发育与抗虫过程的候选基因，为后续的基因功能研究及分子育种工作奠定了重要基础。