Biology Department, The College of William and Mary, Williamsburg, VA, USA.
Plant Signal Behav. 2011 Jun;6(6):850-4. doi: 10.4161/psb.6.6.15203. Epub 2011 Jun 1.
GRAS genes are a large family of streptophyte specific transcription factors that function in a diverse set of physiological and developmental processes. GRAS proteins of the HAIRY MERISTEM (HAM) sub-family are required for maintenance of shoot and root indeterminacy. The transcriptional targets of HAM proteins and the signaling inputs regulating HAM activity are completely unknown. Understanding the relationship of HAM proteins to other members of the GRAS family may inform hypotheses relating to cellular level HAM functions. I here report a phylogenetic analysis of GRAS proteins employing the complete set of known and probable GRAS proteins from the sequenced genomes of the flowering plants Arabidopsis and Rice, the lycophyte Selaginella moellendorffii, and the bryophyte Physcomitrella patens. HAM proteins are most closely related to DELLA proteins, key components of gibberellin perception. However, GRAS proteins diversified into a minimum of twelve discreet monophyletic lineages, including the HAM and DELLA subfamilies, prior to divergence of the moss and flowering plant lineages. Substantial diversification of GRAS proteins at so early a point in land plant evolution suggests that relative relatedness sequence homology among GRAS proteins sub-families may not substantially reflect shared protein function.
GRAS 基因是一类广泛存在于陆生植物中的转录因子家族，在多种生理和发育过程中发挥作用。GRAS 蛋白家族中的 HAM 亚家族在维持茎和根的不定向生长中发挥着重要作用。然而，HAM 蛋白的转录靶标以及调控 HAM 活性的信号输入仍然完全未知。深入了解 HAM 蛋白与 GRAS 家族其他成员之间的关系，可能有助于提出与细胞水平 HAM 功能相关的假说。本研究利用已测序的拟南芥、水稻、石松和苔藓植物的基因组中已知和可能的 GRAS 蛋白数据集，对 GRAS 蛋白进行了系统发育分析。HAM 蛋白与赤霉素感知过程中的关键组分——DELLA 蛋白最为密切相关。然而，在苔藓植物和开花植物分化之前，GRAS 蛋白已经至少分化为十二个独立的单系分支，包括 HAM 和 DELLA 亚家族。在陆地植物进化的早期阶段，GRAS 蛋白发生了如此大规模的多样化，这表明 GRAS 蛋白亚家族之间的相对亲缘关系序列同源性可能并不能充分反映其共同的蛋白功能。
