Abstract

   The homeodomain-leucine zipper (HDZIP) is an important transcription
   factor family, instrumental not only in growth but in finetuning plant
   responses to environmental adversaries. Despite the plethora of
   literature available, the role of HDZIP genes under chewing and sucking
   insects remains elusive. Herein, we identified 40 OsHDZIP genes from
   the rice genome database. The evolutionary relationship, gene
   structure, conserved motifs, and chemical properties highlight the key
   aspects of OsHDZIP genes in rice. The OsHDZIP family is divided into a
   further four subfamilies (i.e., HDZIP I, HDZIP II, HDZIP III, and HDZIP
   IV). Moreover, the protein–protein interaction and Gene Ontology (GO)
   analysis showed that OsHDZIP genes regulate plant growth and response
   to various environmental stimuli. Various microRNA (miRNA) families
   targeted HDZIP III subfamily genes. The microarray data analysis showed
   that OsHDZIP was expressed in almost all tested tissues. Additionally,
   the differential expression patterns of the OsHDZIP genes were found
   under salinity stress and hormonal treatments, whereas under brown
   planthopper (BPH), striped stem borer (SSB), and rice leaf folder
   (RLF), only OsHDZIP3, OsHDZIP4, OsHDZIP40, OsHDZIP10, and OsHDZIP20
   displayed expression. The qRT-PCR analysis further validated the
   expression of OsHDZIP20, OsHDZIP40, and OsHDZIP10 under BPH, small
   brown planthopper (SBPH) infestations, and jinggangmycin (JGM) spraying
   applications. Our results provide detailed knowledge of the OsHDZIP
   gene family resistance in rice plants and will facilitate the
   development of stress-resilient cultivars, particularly against chewing
   and sucking insect pests.

   Keywords: homeodomain-leucine zipper, transcriptomic analysis, brown
   planthopper, small brown planthopper, jinggangmycin

1. Introduction

   The static nature of plants entails the frequent endurance of various
   environmental stresses. In response, plants have developed various
   mechanisms to adjust to the constantly changing environment [[36]1].
   These developmental processes are frequently regulated by numerous
   transcription factors (TFs) [[37]2]. TFs spreads throughout the genome
   and can bond with certain functional cis-elements, facilitating the
   plant’s response to various environmental stimuli. The
   homeodomain–leucine zipper (HDZIP) is a transcription factor family
   that plays a vital role in plant growth, developmental processes, and
   stress response [[38]3]. The HDZIP is a class of homeobox proteins
   containing the homeodomain (HD) and leucine zipper (LZ) motifs
   [[39]3,[40]4]. These two motifs are the signatures of the HDZIP family
   and have been found in all eukaryotic species. However, their
   interaction with a single protein is only found in plants and,
   therefore, HDZIP in Plantae is different than in other organisms
   [[41]5]. Based on their structure, sequence composition, functional
   characteristics, and phylogenetic relationship, the HDZIPs are divided
   into four subfamilies (i.e., HDZIP I, HDZIP II, HDZIP III, and HDZIP
   IV). Additionally, each subfamily has a unique function and forms a
   complex interactive network throughout the plant’s developmental phases
   [[42]6,[43]7,[44]8].

   The HDZIP subfamily I was found to be highly responsive in the
   developmental stages and regulates host plant resistance to several
   abiotic stresses [[45]9,[46]10] and biotic stresses such as pathogens
   and chilling injury [[47]11]. Previously, the vital role of subfamily
   II members was reported to be a very light responsiveness to regulating
   the shade avoidance response and participating in auxin signaling and
   leaf polarity [[48]12,[49]13,[50]14]. The transcription factors of
   subfamily III have an obvious effect on plant development through the
   transportation of various hormones, such as meristem initiation, the
   formation of microtubule tissues, vascular system development, and the
   differentiation of apical provinces [[51]15], whereas the subfamily IV
   members promote the differentiation of epidermal cells in various plant
   organs, trichome and anthocyanins formation, and attributes in fruit
   postharvest to abiotic stresses [[52]8,[53]16,[54]17].

   In the recent decades, rice consumption has increased globally. A
   statistical analysis of rice consumption showed a high increase: in the
   2008/2009 crop year, 437.18 million metric tons (MMTs) of rice was
   consumed; in comparison, in 2021/2022, 509.87 MMTs of rice was consumed
   worldwide. [[55]18]. However, rice crops are targeted by many insect
   pests in, which the most prominent, BPH Nilaparvata lugens Stål and
   Laodelphax striatellus (Hemiptera: Delphacide), are recognized as key
   pests [[56]19,[57]20]. Both BPH and SBPH directly affect rice through
   infestations and, in the process, transmit numerous viral pathogens
   (RGSV) [[58]21,[59]22,[60]23]. Host plant resistance is the most
   efficient strategy for controlling BPH; however, pesticide preferences